Comment 24 for bug 446373

This seems to be related to https://bugs.launchpad.net/pcb/+bug/699251
I don't think it is fixed, it is only hard to reproduce.
We just ran into this with an in-house application that has no relation to xsane. Basically, whenever a throbber is displayed, we get a crash.

This happens only on one machine which is distinct by
* Using the proprietary nvidia driver
* Having XINERAMA enabled (as opposed to the nividia-specific dual-screen support)
* Has one screen with the usual orientation and the other rotated by 90°

I believe this to be a bug in the Xrender support somewhere (libXrender, Server module, nvidia driver?)
It also does only happen sometimes and may be related to reparenting the throbber on another wizard page in our case.