You need to edit the Registry to sort out this one.
So my instructions assume that you are confident and experienced with this.
Close down your PC completely (not Sleep or Hibernate)
Start your PC in Safe Mode (tap the F8 key repeatedly from switch on until you get a black screen to select it).
Login to any Administrator account and enter Password if requested
It might tell you that it has used the default profile - that's OK.
Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
User profiles are the items with a long string of numbers.
Find the right one by looking at ProfileImagePath
There should be a .bak version of the faulty profile
Rename the non bak one to .ba
Rename the bak one to remove the .bak
Rename the .ba one to .bak
Select the new non bak one and change RefCount to zero and State to zero
Close Regedit and reboot