Recently I had a major problem on my Win2003 server running IIS6, I am using ISAPI rewrite version 3 and use a text file that maps the URL's to the ID's.  For some weird reason, IIS was caching the text file even though when I downloaded the URL list it was definitely the new updated version - It would work fine if I restarted IIS, but that's a real pain in the arse to have to do that every time a new product / page was added or updated!  More...