Re: Segmentation Fault in glGetString() with Dual-Video Cards
glGetString() might segfault in good faith if there were no active GLX context, say.
For example, before the window was created, or (depending on toolkit) if you call it outside of the display-callback or similar. Could that be the problem?
You might try calling glXGetCurrentContext() and see what it returns -- or whether it seg-faults too.