Roaming Profile, Offline Error?

Hi,
I have a Server running Windows 2003 Server which is my Domain.
Ive trying to setup Roaming Profiles for my users. Ive setup Home Directors and User Profile shares already. And for the users who are going to be mobile and work offline Folder Redirection for their My Documents. Now my issue is when they logon offline and logoff they get an error
“Windows cannon Update your roaming profile. Possible causes of this error include network problem or insuffcient security rights. If this problem persits contact your administrator.”

Why is it doing that?