SimpleLogoff is an open source freeware application for one click logoff from Windows. Download link: https://skydrive.live.com/redir.aspx?cid=b4508367face85d1&resid=B4508367FACE85D1!215&parid=B4508367FACE85D1!134
By executing this application you are logged out without any questions asked.
The application is portable, no any setup needed. The source code is included.