Ok, I think I know what happened, because it happened to me this morning.
- System update runs, installs new kernel, new nvidia-libs that aren't compatible with the currently running kernel
- MAME (and anything else using GLX) shows only a black screen (although -video soft worked for me)
- Rebooting fixed it, because now you're on the newer kernel
Yes, we've reinvented DLL hell ;-)
Ah, OK

!