Same problem here I think - after I updated, lobby crashed, and crashed whenever I tried to start it. Renamed the .bak file and it seems to be working so far.
(EDIT: Windows 7. It was working about 12 hours ago.)
I guess I'll wait to run the benchmark until after this is resolved. (Not that it would make any difference to Spring I imagine, but it's a bit of a headache.)
EDIT 2: When I allowed it to restart after updating it's started crashing again. Lovely. At some point a message saying the following popped up:
"This program requires a missing Windows component
... (blah blah blah) ...
This program requires flash.ocx, which is no longer included in this version of Windows."