Anybody else have to reboot regularly?

We are running Orion v6.39 on Win2000-SP3. We've upgraded a couple of times since 6.0 and with each version we've had difficulties with the website dying every 4 to 8 days. The way it happens is when a user logs in they get a standard IIS error page. It begins happening only once in a while, but gradually gets worse until it fails nine times out of ten. Restarting the IIS Web Services helps for a while, but the only way we've found to really make it improve things for any length of time is to reboot the server.

It seems to be an issue with IIS, but it isn't one we ever had with Orion 2002. The IIS web logs have been no help.

Anybody else having similar problems, or know of a solution?