Server 2008, IIS 7, URL Rewrite, and 404s…

I recently migrated my wordpress blogs from Server 2003 to Server 2008. This was for the purpose of using pretty permalinks with URL Rewrite under IIS 7.

So far so good, everything is mostly working.

The only problem I’m still having pertains to wordpress 404s. When I try to go to a blog post that doesn’t’ exist, I get a 500 internal server error. This happens whether or not I have /index.php/ trailing my URL or not, so I don’t think it is related to my URL rewriting.

I had this problem on 2003 as well, only then I got an IIS 404. I handled this by using a custom 404 that was actually designed to get around mod_rewrite, but also solved this problem.

So, I ask: has anyone else seen this? It seems too consistent to be a fluke….any theories about what is happening?

Applicable sites:
https://clifgriffin.com
https://prolutum.com

Thanks in advance,
Clifton