I get this problem too, on Feisty Kubuntu with AMD64 and nVidia X driver. I have a feeling it is related to that.
However I have found a workaround that works every time and that suggests to me it is something in the environment. When this starts happening I get "Segmentation fault (core dumped)" whenever I try to start Firefox from the shell, and it also won't start from the menu. However, if I ssh to localhost, and then start it from the shell there it works fine!
So I am sorted for now, but this is annoying. Short of using this trick, only restarting the X server or rebooting fixes the problem. Firefox is a pretty essential app so I hope this gets fixed soon. Let me know if I can help.
I get this problem too, on Feisty Kubuntu with AMD64 and nVidia X driver. I have a feeling it is related to that.
However I have found a workaround that works every time and that suggests to me it is something in the environment. When this starts happening I get "Segmentation fault (core dumped)" whenever I try to start Firefox from the shell, and it also won't start from the menu. However, if I ssh to localhost, and then start it from the shell there it works fine!
th@shuttle:~$ firefox
Segmentation fault (core dumped)
th@shuttle:~$ ssh localhost DISPLAY=:0 firefox
<firefox pops up!>
So I am sorted for now, but this is annoying. Short of using this trick, only restarting the X server or rebooting fixes the problem. Firefox is a pretty essential app so I hope this gets fixed soon. Let me know if I can help.