Your user profile may be corrupted.. search for the ntuser.bak and the ntuser.dat hidden files in your user profile folder. Next rename the ntuser.dat to ntuser.old and ntuser.bak to ntuser.dat
If that doesn't work, another approach is to create a new user account and migrate your files and settings with a registry edition in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders. Will complete this info if you need it.
BTW, this is for XP but should work as well with W7