I had this problem few days ago and most "solutions" called to create a new user account. yet sometimes it is an unnecessary , to broad action. In my case it was a (self edited) windows style which caused problems.
Symptoms:
- when i try to log onto a specific account i get thrown back to logon screen
- i can log into this account in safe mode
- there is no suspicious entries in autostart, virusscan is clean too
- i do use third-party windows styles via UxStyle or Uxtheme Multipatcher