Okay - time to break open the toys!
Can you please download, install and run the SBS 2003 Best Practise Analyzer which should identify any glaring problems with your server.
http://www.microsoft.com/downloads/details.aspx?familyid=3874527A-DE19-49BB-800F-352F3B6F2922&displaylang=en
Report back with anything found please or if you need more assistance.
Thanks - Alan