How big is the group? Also, you should post more information as Brian
suggested - it would be very helpful.
1) Outlook version
2) E-mail environment (POP3, Exchange, etc.)
3) Are you using a PST? How large is it?
4) Are there any error messages and more specifically, error numbers?
5) What steps have you taken to try to resolve the problem so that we don't
waste time telling you to do the same thing?