Login screen not working correctly (again)

[amips]

Running Windows 7 Home Premium 64 bit on new desktop with 4 Users. 2 weeks ago (after running OK for nearly a week) we found that when (anyone) clicked on their login icon, it "depressed" but nothing else happened - i.e. no password request for those who'd set one up, or loading of desktop for others. Clicking anywhere onscreen resulted in no action. I found that by clicking a user account that did not have a password set up on it, then pressing ENTER, resulted in normal action of desktop loading and PC operating normally. Couldn't fix other password protected accounts so I reformatted it and all was well until..........NOW!

It's started to do it again - what on earth is causing this - ran MBAM, AVG and SAS but no malware detected??.

[RandyL]

User Profile corruption evidently. Constant file corruption could be a sign of a failing drive but since this is the User Profile again I doubt it. I've seen AVG do some pretty strange things so perhaps that.

[Plastic Nev]

Which firewall are you using? I have seen some strange things suddenly being blocked by the firewall after some of the windows updates as well.

Nev.