|i posted a question like this a little while ago - our Exchange server was paging over 8GB.|
unfortunately, all I've been able to come up with is "leaky apps." Plenty of poorly written applications (including microsoft products, including the OS) are written in such a way that they do not "release" the RAM they were using when they are done with it. obviously, this'll fill up all your available ram quite quickly. The only thing i've come up with so far is rebooting the server at night periodically.