Myself and several other users have been experiencing hard locks in Edgy (i.e. the system becoming completely unresponsive to any mouse or keyboard input - including Ctrl+Alt+Delete and Ctrl+Alt+Backspace). People's precise symptoms differ somewhat, and are documented in this forum thread on the Ubuntu forums: http://ubuntuforums.org/showthread.php?t=296031.
In my particular case the symptoms are different each time - the hard lock has so far happened:
- while doing nothing in particular and hovering the cursor over the icons in the top-right of the screen.
- during a Skype call.
- while using Azureus.
I don't have anything particularly out-of-the ordinary on this machine, so it's pretty much an up-to-date Edgy install, plus a few fairly standard programs (e.g.. Sun Java, Azureus, Skype, video codecs, ...). The hardware is a laptop (Acer 1357LMi) with Athlon XP-M 3000+ CPU and ATI Radeon Mobility 9200 graphics.
I'm afraid I can't be particularly helpful in terms of a reproduction scenario (as I say, the problem seems to be somewhat random - though many others are hitting it). I'm happy to reproduce this myself and produce any useful information if someone can tell me what to gather here. The frequency of this bug seems to be that it now mostly happens within an hour of booting - enough to make the OS pretty much unusable for everyday use so I'm back on Windows.
Well, following the suggestions in the forum thread above, I tried to change to using the i386 kernel rather than the generic version of the kernel. That seems to have fixed the very frequent hangs I was seeing. This has also resolved the problem for at least two of the other people who were experiencing this, so it looks likely that this bug is present in the generic, but not in the i386 kernel.