There was a problem importing the global list: TF26204: The account you entered is not recognized.

If you got the error "There was a problem importing the global list: TF26204: The account
you entered is not recognized." while trying to import a global list file then probably one of the items in the lists contain backslash and TFS considers this value as a user name... I got this while entering the value 800\40. Funny!