Yosemite stuck on login screen

[yitbos]

I upgraded my MacBook Pro to Yosemite today. The install seemed smooth, it restarted, then after I put in my password at the login screen, got the beachball. I let it go for a couple hours, and nothing changed. Tried resetting PRAM, tried holding down the power button reset, tried completely reinstalling the OS, tried safe mode; all the same result. I read on one forum that some people had a simliar issue when they were running betas, and that they found the problem to be the GPU switching, and that to fix it they connected an HDMI adapter to an HDTV screen...did that, did not work for me. I tried opening Disk Utility and repairing disk permissions, that also did not work.

Has anyone else had the same problem that has found a fix for it?

Thanks