Windows 7 crash/freeze during login

My computer is crashing during the login process. I type in my password, then it goes to the blue "welcome" screen, with the rotating icon. The screen briefly flashes, and then a few seconds later freezes completely. Not a BSOD exactly, but still unresponsive, and never gets to the main desktop.

I can get it to start in Safe Mode, so I checked that all drivers were up to date (they are). I also used msconfig to stop extra start up drivers, without effect. My boot diagnostics and start up repair say there's nothing wrong. I have implemented a system restore without success. I've also used fsecure online to check for viruses and it's come up empty, and I don't want to reinstall without knowing what's causing this problem.

Yesterday, it was working fine, although the Nvida driver crashed once and recovered (it was my first suspect, but the driver is up to date). I haven't made any changes to my system recently but I've had this problem before and it suddenly resolved itself. This time I'm not so lucky. Does anyone have any suggestions, please?

64-bit Windows Home Premium, original OEM. Purchased July 2011.

If you are able to start the system in Safe Mode, then, it seems to me you have a problem with Auto Run at Start Up of some software you have installed on your machine.
You can try to disable in Safe Mode everything that starts automatically (I mean the software which you installed, not the system elements :). Do not forget to clean the registry as well.

Hope my answer was of any help.