WOOOOOHOOOO !!!
I finally managed to track down the infamous ATI crash bug which makes the viewer crash Linux solid every few minutes... It is the result of a bug (or missing work around for a hardware bug) in the fglrx driver (the open source radeon driver is not affected and successfully works around this hardware bug, but alas the open source drivers does not support the recent ATI chips).
You will find the full details as well as a patch here:
https://jira.secondlife.com/browse/VWR-1320
Enjoy !