During Restart Computer Stalls At Shutdown

When I do a "restart", on the computer screen I could see "log out", a few seconds later, "shutdown." At this point, the system stalls at "shutdown." I waiting for over 5 minutes, and it was still stalled at "shutdown." To continue working with my computer, at the ""Shut down stall", I remove the power cord from my computer. About a minute later, I reconnect my power cord and click the power button. After that there is no problem. Except when I do a "Restart."