Take a look at How to get the taskbar and desktop back
and see if that fix will set you right.
If not, the user account may be scrunged up somehow.
Easiest (if you can) would be to remove the user and re-add it.
I haven't done this in a while but I think you can save your settings folders (desktop, favorites, etc) before removing the account and then after you have a new account created, log on as another user /w admin rights and put the saved folders in the new account replacing the blank ones created with the new account.