I should clarify, that upgrading the kernel may only resolve the full system lockup. The first issue you noted where there is a brief, recoverable lockup may very well be a different and unrelated bug.
Since it sounds like your company's OpenGL based modeling code is the only reliable reproduction path, would you be able to provide me with that code (or a compiled binary, if that is more acceptable) so that I can attempt to reproduce this? You can email it to email@example.com
if you're not comfortable with posting the code here.
If you'd prefer to wait until after you've tested a 2.6.12.x kernel first, that's fine too.