In my case, which is a SQL2008 R2, I successfully shrank the tempdb by using Method 1 in MS KB

http://support.microsoft.com/kb/307487

A little bit tricky part is I didn't logon by using SA. I do have sysadmin privilege therefore when system asked me to restart by using command line, I hit Ctrl-C to quit and start the SQL services in Management Console.

BTW, I did above on a dev box.