Hmmm, no change.
Off to recheck the way X's module handling was configured...
If anyone has any other ideas, I'd love to stop responding to myself
__divdi3 is exported properly (at least, nm can find it) by /lib/glibc-2.2.5.so, which is symlinked to /lib/libc.so.6, so might it be that libGLcore is statically linked, and therefore not seeing libc?
... on second thought, if it was statically linked, it'd have __divdi3 in itself. Not to mention, no one else would be able to run it if that was the problem. Hmm..... I'm hoping that recompiling X against the proper libc will fix things. <crosses fingers>