Windows 7 SP1 login screen freeze

When login screen appears, both mouse and keyboard aren't working.

I do shutdown via powerbutton, Windows 7 notices that and changes screen to 'Shutting down' spinner. Once rebooted, freezes once again.

However, if I don't allow 'clean' shutdown, by keep pressing power, on next boot up all works -- I can login and every app seems fine.

Only events of 'Error' type I see in Event log are:

1. Application subnode: Event filter with query "SELECT * FROM __InstanceModificationEvent WITHIN 60 WHERE TargetInstance ISA "Win32_Processor" AND TargetInstance.LoadPercentage > 99" could not be reactivated in namespace "//./root/CIMV2" because of error 0x80041003. Events cannot be delivered through this filter until the problem is corrected.
2. System subnode: SAM failed to start the TCP/IP or SPX/IPX listening thread.

Motherboard is Gigabyte GA-Z97X-UD3H, BIOS ver F4. As I've said, once logged in, everything works fine, so it's not a processor or RAM, or video, or hard drive.

What could it be?

UPDATE Safe mode does not help after clean shutdown: login screen appears at lower resolution, but input devices still not working. Interestingly, even screen suspension works -- I've left system for ~10 min and screen gone to sleep (and woke up after I poked power button).

Thank you!

Unless I'm misunderstanding, you're not performing a "clean" shutdown, it's call a Hard shutdown/reset. (Where you press and hold the power button to get it to shut off.) If this is in fact the case your HDD likely has bad sectors on it that can easily be repaired, for free, by using a bootable repair disc, running chkdsk when you can get to the desktop, etc...

You mention it's not hardware, have you run any diagnostics tests? Or is "once logged in, everything works fine" your diagnosis so far?

I recommend:

~ Running bootable or live software to double check your hardware, mainly the HDD.
~ Run basic repair commands like chkdsk, sfc /scannow, bootrec.exe /fixboot
~ Try what's literally called a clean boot through MSCONFIG