I’ve seen this happen recently at my job and it actually happened to me directly.  Being in Support I have to be apart of many groups.  While I was setting up a new machine I noticed none of the Group Policies were applying and certain drives I normally access were now throwing a ‘Access Denied’ error.  After discussing it with some colleagues we determined I was a member of too many groups.  Increasing the default Token Size to 48000 was recommended.  This is a very simple fix and we decided to apply it to our default machine policy for our Domain.

Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters

Entry: MaxTokenSize
Data type: REG_DWORD
Value: 48000

If you are having symptoms where your group policy is not applying or a group membership isn’t taking effect try this out.

To learn more about this check out this Microsoft Article: http://support.microsoft.com/kb/327825