Many Maemo developers have noticed that the version of Xephyr (xserver-xephyr) on Ubuntu Jaunty crashes very easily, making the SDK nearly useless. I uploaded a Xepyhr version to the Openismus PPA with the patch applied to fix the crash. Maybe one of the open launchpad bugs is relevant.
I wouldn’t generally advise you to upgrade to Ubuntu Jaunty anyway, certainly not if you have Intel graphics (for instance on my Lenovo X61) – ironically the very graphics hardware that you’d expect to work with Linux.
Do any of the suggestions on https://wiki.ubuntu.com/X/Troubleshooting/IntelPerformance help you with your problems? I haven’t noticed any problems with Jaunty on my laptop (a Thinkpad X60s), but perhaps the problems don’t occur on the older Intel chips. I am not running compiz though, so if your problems are related to that I might have just avoided them.
I had the X freezing and it seems to have stopped with linux kernel 2.6.30-rc8 and xserver-xorg-intel >= 2:2.7.99.1-2… But then I have to admit that it’s the most unstable that Debian/sid was in years, so it’s only reasonable to expect it in Ubuntu as well.
Hm, is there some kind of stress test for the i915 module? I’d like to be *sure* it’s driver-related, and not have to wait until it magically fixes itself. I even had X freezes without using Compiz.
FWIW my X crashes were invariably with firefox working on the combobox part of the URL entry field. I use the halfbaked tritium window manager and no glamor whatoever.
SSHing into the computer dmesg showed “wedged hardware” which should be something no application should be able to achieve without help of the driver.