I had exactly same problem a few weeks ago - here was my fix-
Goto system console at the server. Type in NWCONFIG, select NCF File Option, Edit Autoexec.ncf. The line saying 'Start of Daylight Savings = March Sunday Last' was fine, the line saying 'End of daylight savings said >=23 October. This was changed to 'October Sunday Last'. The server was rebooted (may only need to reload grpwise.nlm) Groupwise now shows the correct time.
Hope it helps