I am pretty dumbfolded on this one and there seem to be virtually no clues around the net. The only thing vaguely related is a fairly similar (unsuccessful) question on reddit:
I am running Mathematica 8 using a school licence server - it crashed the other day because my VPN session ran out. After that I have no longer been able to launch successfully.
Multiple uninstall / registry clean attempts have remained unsuccessful - any ideas / suggestions?