I have Ubuntu 12.04 running on VirtualBox under Windows 8. I've had it for about a year now and have had no problem whatsoever. A few nights ago, out of nowhere and while I was in the middle of working on my windows machine, I saw Ubuntu (which is running on a 2nd monitor) crash. Basically the screen went black, tons of text appeared and disappeared before I could read any of it.
After a restart it asked me to check the file system and then it boot up to a login screen I've never seen before, as I always had it log in automatically. Now, when I type my password, the screen turns black for a second and then brings me back to the login screen.
I know my password (I am able to login when pressing ctrl+alt+f1), but I don't really know where to go from here. I was able to follow some instructions on uninstalling VBox Additions but that did not help. It's important to specify that nothing changed on the host or the VM for a long time (it was probably running for a month straight when that happened).
Any help would be appreciated. I don't want to upgrade to 13 or 14 unless it's absolutely necessary.
thanks in advance!
Update: I'm also unable to log in with Guest. I have tried different desktop environments (2D, Unity, etc) and the same happens in all of them.