2K3 Standard Server, Domino Issues

I am running a dual xeon xSeries with Windows 2K3 Standard Server as my email server for the office. THe only other software that runs on it is Lotus Domino (the actual email client database) and Blackberry Enterprise (for the routing of email to the staffs Blackberries). I have begun to have an issue with my server lagging out and crashing for what seems to be no good reason. It has plenty of resources, and the performance moniter shows little to no activity while it is crashing. Does anyone have any ideas?