We seem to be getting a lot of 500 Internal Server Errors lately, they
suddenly happen and then stop.

We have BM37SP2 with an updated Proxy.Pac from Craigs site. We have tried
putting a stock Proxy.Pac in to test that, with no luck.

A Proxy -cc is run every time the server boots to clear the cache.

We also have loaded and unloaded Linkwall to rule that out.

Any thoughts on where they could be coming from?