your main profile is somehow corrupt and cannot be loaded.
Best course of action that I see is:
create new profile
copy everything you can/want over from old profile to new
c:\users\<profilename>
log to new profile, after which you can try to log on the old profile if you want but I think in most cases it is a lost cause.
what you lose:
theme you were using, some program customization and that is pretty much all.