Crash on certain websites

Thank you for taking the time to report this bug and helping to make Ubuntu better. However, according to this report, you are not using the most recent version of this package for your Ubuntu release. Please upgrade to the most recent version and let us know if you are still having this issue. Thanks in advance.

Versions:
Ubuntu: ubuntu karmic 32bits (compiz enabled)
Firefox 3.5.8+build+nobinonly-0ubuntu0.9.10.1
libglib 2.22.3-0ubuntu1

Errors:
(firefox:17750): GLib-WARNING **: g_set_prgname() called multiple times
(firefox:17750): GLib-GObject-WARNING **: invalid unclassed pointer in cast to `GtkObject'
(firefox:17750): GLib-GObject-WARNING **: invalid unclassed pointer in cast to `GtkObject'
(firefox:17750): GLib-GObject-WARNING **: invalid unclassed pointer in cast to `GtkObject'
(firefox:17750): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer
(firefox:17750): GLib-GObject-CRITICAL **: g_signal_handler_disconnect: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed
(firefox:17750): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer
(firefox:17750): GLib-GObject-CRITICAL **: g_signal_handler_disconnect: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed
Segmentation fault

Sometimes I could reproduce the crash:
* Enter gmail and righ-clicked in a link inside a message.
which may rule-out the "flash" related problem...? (as gmail does not include flash objects)

However several times in different sites have crashed.

I'm not sure if the installed plugins are somehow related as when I disabled all of them it didn't crash (I performed few tests).
I activated one by one and test it again... but it was not consistent. However I found that somehow when I deactivate "Flashblock" plugin crashes didn't happen under the same situation, but I can't be 100% sure.

All those errors can be seen also when firefox is restarted after the activation/deactivation of a plugin.

Thank you for the extra information. However, it looks like you are using Firefox from a PPA that is not supported by Ubuntu. Could you please let us know what PPA you are using for Firefox?

I'm using "karmic-updates" repository: http://packages.ubuntu.com/karmic-updates/firefox-3.5
I don't have ubufox installed.
Since my last post, I have been using firefox without the "Flashblock" plugin but unfortunately firefox
still crashes. I have noticed that usually it crashes when clicking a link or displaying the "right-click" menu.
Even it have crashed in pages without any Flash content, I also noticed that it is more frequent when
they have flash content or the previously-loaded page had flash content.

I found a page where 100% of the times crashed. I disabled ALL plugins and still crash. This is how:
Enter this site: http://tenki.jp/forecast/city-38.html?selected=tenki&date=0
Then in the links at the middle (4 columns around 16 rows), where it says: (ピンポイント天気) (its in japanese), click in any of those. Then in the page that opens, click again in any of the same list of links. In my case, it crashes. As noted, this page uses many flash objects. I hope it helps.

Switching back to the 'firefox' package since we are no longer separating Firefox bugs based on version.

@Lepe
I followed the directions you provided and Firefox 3.7 on Ubuntu 10.04 did not crash. Could you please run the following command in a terminal:

apport-collect 510548

This will automatically add information about your system to this report so we can more easily determine the cause of this bug. Bear in mind that you may need to install the python-launchpadlib package from the universe repository. Additionally, when prompted to give apport-collect permissions for Launchpad you will need to give it at least the ability to "Change Non-Private" data as it will be adding information to your bug report. Thanks in advance!

I tested in other computer with Xubuntu karmic 64bits and firefox 3.6.3pre running, and It didn't crash.

Then, I installed the svn version 3.6.3pre (3.6.3~hg20100327r33760+nobinonly-0ubuntu1~umd) from "http://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu karmic main" repository and still have the same (crashing) behavior. I will perform the "apport-collect" report in this moment.

Thank you.

Architecture: i386
CrashDB: ubuntu
DistroRelease: Ubuntu 9.10
FirefoxPackages:
 firefox 3.6.3~hg20100327r33760+nobinonly-0ubuntu1~umd1~karmic
 firefox-gnome-support N/A
 firefox-branding 3.6.3~hg20100327r33760+nobinonly-0ubuntu1~umd1~karmic
 abroswer N/A
 abrowser-branding N/A
Package: firefox 3.6.3~hg20100327r33760+nobinonly-0ubuntu1~umd1~karmic
PackageArchitecture: i386
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_US.UTF-8
ProcVersionSignature: Ubuntu 2.6.31-20.58-generic-pae
Tags: ppa
ThirdParty: True
Uname: Linux 2.6.31-20-generic-pae i686
UserGroups: adm admin audio cdrom dialout dip floppy fuse lpadmin plugdev video

I tested with Firefox 3.6.3 on my Ubuntu 10.04 system and still was unable to reproduce this crash.

Sometimes Firefox profiles can become corrupt and/or extensions can conflict. Could you please try this with a new profile and see if the problem still exists? You do not need to delete your old profile to test. If this helps, you might want to try to disable all your extensions and re-enable them one by one until you find the problematic one.

You can start the profile manager with the following command:
firefox -ProfileManager

Hi Draycen, I created a new profile and even renamed the ~/.mozilla directory and still happens.
As a note, If it doesn't crash after the second click, try a third or fourth click in the same list of links.
You are using 10.04 while I'm using 9.10. I will try other ways to debug the error if possible and be
back as soon I have something to report. Thank you.

I installed firefox-dbg ant tried to debug the error using gdb (I followed the instructions in other post as is the first time I use gdb). This is the output:

$ firefox -g
sh /usr/lib/firefox-3.6.3pre/run-mozilla.sh /usr/bin/gdb /usr/lib/firefox-3.6.3pre/firefox-bin -x /tmp/mozargs.oOAzUP
GNU gdb (GDB) 7.0-ubuntu
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/lib/firefox-3.6.3pre/firefox...Reading symbols from /usr/lib/debug/usr/lib/firefox-3.6.3pre/firefox-bin...done.
(no debugging symbols found)...done.
(gdb) set args -a firefox --sync
(gdb) break gdk_x_error
Function "gdk_x_error" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y

Breakpoint 1 (gdk_x_error) pending.
(gdb) run
Starting program: /usr/lib/firefox-3.6.3pre/firefox -a firefox --sync
[Thread debugging using libthread_db enabled]

(firefox:2856): GLib-WARNING **: g_set_prgname() called multiple times
[New Thread 0xb53ffb70 (LWP 2860)]
[New Thread 0xb4bfeb70 (LWP 2861)]
[New Thread 0xb43fdb70 (LWP 2862)]
[New Thread 0xb36ffb70 (LWP 2863)]
[New Thread 0xb2cffb70 (LWP 2864)]
[Thread 0xb2cffb70 (LWP 2864) exited]
[New Thread 0xb2cffb70 (LWP 2865)]
[New Thread 0xb17bdb70 (LWP 2876)]
[New Thread 0xb0fbcb70 (LWP 2878)]
[New Thread 0xafc58b70 (LWP 2884)]
[New Thread 0xaf457b70 (LWP 2886)]
[Thread 0xb0fbcb70 (LWP 2878) exited]
[Thread 0xb2cffb70 (LWP 2865) exited]
[Thread 0xb17bdb70 (LWP 2876) exited]
[Thread 0xaf457b70 (LWP 2886) exited]
[New Thread 0xb2cffb70 (LWP 2953)]
[New Thread 0xb0fbcb70 (LWP 2954)]
[New Thread 0xaf457b70 (LWP 2966)]
[New Thread 0xb17bdb70 (LWP 2980)]
[Thread 0xb17bdb70 (LWP 2980) exited]
[New Thread 0xaafffb70 (LWP 3003)]
[Thread 0xaafffb70 (LWP 3003) exited]
[New Thread 0xaafffb70 (LWP 3007)]
[Thread 0xafc58b70 (LWP 2884) exited]
[New Thread 0xafc58b70 (LWP 3009)]
[New Thread 0xb17bdb70 (LWP 3010)]
[New Thread 0xa9affb70 (LWP 3011)]
[New Thread 0xa92feb70 (LWP 3012)]
[New Thread 0xa77ffb70 (LWP 3013)]
[Thread 0xa77ffb70 (LWP 3013) exited]
[New Thread 0xa77ffb70 (LWP 3017)]
[New Thread 0xa56ffb70 (LWP 3018)]
[New Thread 0xa40ffb70 (LWP 3019)]
[Thread 0xa40ffb70 (LWP 3019) exited]
[New Thread 0xa40ffb70 (LWP 3020)]
[Thread 0xa40ffb70 (LWP 3020) exited]
[New Thread 0xa40ffb70 (LWP 3021)]
[Thread 0xa40ffb70 (LWP 3021) exited]
[New Thread 0xa40ffb70 (LWP 3022)]
[Thread 0xa40ffb70 (LWP 3022) exited]

(firefox:2856): GLib-GObject-WARNING **: invalid unclassed pointer in cast to `GtkObject'

(firefox:2856): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer

(firefox:2856): GLib-GObject-CRITICAL **: g_signal_handler_disconnect: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(firefox:2856): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer

(firefox:2856): GLib-GObject-CRITICAL **: g_signal_ha...

Could you please generate an apport crash report for this?
You can enable apport for one instance like this:
sudo service apport start force_start=1

I am marking this invalid as apport will open a new bug when the crash is generated. If it does not, you can reset the status of this one to New and we will try something else.