Help - MacBook Pro only displays wallpaper after login (and this is only happening with one of the user accounts)

I turned off my MacBook Pro when Safari completely froze on my screen. When I turned my computer back on, I was able to log in as normal. But the only thing that was displayed was the wallpaper and my working mouse pointer (and nothing else).

I have tried to boot in safe mode, with the same result. However, I am able to log in normally to my guest account and it works completely fine!

I unfortunately do not have any of the installation discs.

Any suggestions on how to fix this?

(MacBook Pro with OSX Yosemite Version 10.10.2)