Xubuntu8.04 beta firefox,opera..:segmentation fault

freelxs

The latest firefox ,opera and firefox-2.
When I start the firefox-3, it will broke and say "segmentation fault".
Opera and thunderbird also do that.
Firefox-2 can be open,but it will broke when pop-up a dialog.
I have update the new system,but it's also.
I hava search this forum, but I cant's find the answer.
May you help me?
Thank you!