Try this --
Warning you will lose any customisations doing this. --
At the login screen do:
Alt & Ctrl & F1, now log in as yourself.
Type:
then press enter. (this makes a copy of your current .kde4 folder and renames it)
Now type:
and press enter. (This will delete your current .kde4 folder)
Type:
exit and press enter
Now do:
Alt & F7
Login as normal. If all is ok you can delete the .kde4old folder.