Several Ubuntu 8.04 fglrx users are reporting a persistent, predictable, repeatable xorg crash when using an x1600/x1400 configured with dual monitors and BigDesktop. To make X crash completely, all you need to do is click on the secondary desktop background. The crash only occurs when compiz-fusion is enabled. Everything is fine when Desktop Effects are disabled.
And we have been told that this is the place to talk about it. Please let me (or anyone else involved in the above launchpad thread) know what we can do to help diagnose and resolve the bug.
I also can reproduced this bug. I switched to Metacity and it went away. It is not a single click on the second desktop for me. I have to click between the desktop and a window about 3 times and X will crash every time.