I found a workaround!
It seems the bug can only be reproduced with vga (as opposed to framebuffer) terminals. With the kernel using vesafb, I can't make it crash anymore.
I'm now using xorg-core 1.3.0, intel 2.1.0, mesa 6.5.3, kernel 2.6.22-rc7.
With the regular vga terminals, the same crash occured every once in a while, even if any GL apps hadn't been used.