Windows 7 keeps locking up

After about 20 seconds of starting my PC up Windows 7 locks up. I can still do some things like if i have a firefox window open i can browse but thats about it. I cant open anything. This has only just started today

Any help on this?

Restored my PC to yesterday after starting up in safe mode and it appears to have fixed it. The updates i installed yesterday must of caused it. Edit: Just ran a malware/spyware scan to be sure and they picked up a few things, dont know if that was the cause of it though. One thing in particular was "Relevant Knowledge" what monitors your web usage.