Client logon to domain hangs when mapped file server is off line

I have a Windows 2003 R2 Server acting as my file server in a AD network.  Users have a login script that maps two folders to their computer.  A Home folder, located on the file server is also mapped to a drive letter from the profile of their AD account settings.  When the file server is taken offline, any computer trying to logon would hang and their desktop would not load or take a very very long time to load.  The domain controller is a seperate server.  What could be causing this and how can this be changed to still allow the user to login and use other network resources, but not hang if the file server is offline?

Thanks!