The Limit profile size Group Policy setting does not take effect on a client computer that is running Windows Vista or Windows Server 2008 if a user profile size is greater than 4 GB
In an Active Directory domain environment, you configure the Limit profile size Group Policy setting to manage the size of user profiles. On a Windows Vista or Windows Server 2008-based client computer, if the user profile size is more than 4 GB the Group Policy setting does not take effect. You do not receive a message that the profile size is exceeded, and you can log off as usual even if the Max Profile Size field of the Group Policy setting is set to a value less than 4 GB.
When you use a roaming profile, you receive the following message:
Your roaming user profile was not completely synchronized. See the event log for details or contact administrator.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB971347.