My newly clean installed Win 7 64 system has a developed a very peculiar user profile login problem. When logging on from starting the system, I can login to a user profile no problem. It is when I log out of that profile and attempt to login to another profile that the fun starts. As soon as the profile login screen appears, the password dialog box immediately fills itself in. If I delete it and attempt to type in the correct password, the box immediately fills itself in again. It seems to be using a single letter, such as 'c', 'u', 'g' which I suspect may be related to windows looking for the drive that the password reset information is on, but I'm not sure. Very bizarre behaviour. I can only get out of it by rebooting, which allows me to login properly. It doesn't do this all the time but does do it frequently. Any ideas how it may be cured?
Sounds to me like you have a keyboard and/or mouse driver issue going on. If you have any "drivers" for your keyboard and/or mouse then I would suggest uninstalling them. Don't worry, you should still be able to use your keyboard and mouse but you probably won't have any extra functions like certain hot keys or even certain buttons on your mouse might no longer work - but you should at least still be able to use them. Of course, reinstalling drivers for a mouse and/or keyboard theoretically will enable those extra abilities but you might also have that weird problem again too. (Have you obtained the latest drivers?!)
Aside from that, you might also look into any other input devices you may have hooked up to your computer like scanners, joysticks, and/or possibly even old dial-up modems. And that's just for starts. The list of input or even output devices is pretty long but reducing your computer to it's most basic elements with just a basic keyboard and basic mouse is where I'd at least begin the troubleshooting process. And if your keyboard/mouse are USB devices you might also look into your BIOS settings too (again, that's a bit too borad a topic to go into here).
Hope that helps a little, anyway.
No solution, but for some advice on debugging see: Troubleshooting the Windows logon process.
This uses information from this Microsoft Support article :
If this gets you any useful information, please post it.
You can also try to check your system using sfc /scannow.
1) Try Repairing windows 7 installation
For more information regarding repairing Win7 ,
2) Try deleting that account and creating a new one
3) Try removing password for that account and then putting it again
4) Scan for any type of winlogin virus