Cant switch user accounts in Ultimate 64

Now this is the first time that i have loaded a 2nd profile on my laptop. I have the same version on my desktop and it works without any issues. But on my Sony Vaio laptop i cannot get fast user switching to work at all. I have worked ont his for 2 days now. Ive tried all the forums and all the little hacks for regedit, gpedit...etc etc. Nothing is working.... does anyone out there have a fix for this or am i just doomed to have to log off when i want to switch accounts?

go to start and type in search cmd and run as administrator and run "sfc /scannow" without quotes and see if you have integrity violations it could also be that the user profile is corrupted and may need to be replaced. First things first though..