I wish you'd be more specific -it's so frustrating. We're here and you're on the PC in question./
Exactly what does it mean " the system won't log me in"? Same error? Or it won't accept your own credentials? If it's not the original DLL problem in Safe Mode, log on as Administrator without a password.
If you can do that, edit your registry (after saving it via File/Export/Entire Registry) by navigating to
and deleting the GINADLL key. This is a fairly well reported and documented problem so if you're not infected, one of the solutions offered ought to work.
The consensus on the web seems to be that Broadcomm Wireless adapter is involved here.