Try to enable FREB "to figure out what exactly is happening with your requests" http://learn.iis.net/page.aspx/266/troubleshooting-failed-requests-using-tracing-in-iis7/

I was recently tasked with moving a site from JSP to .Net. As part of our contract with a sub contracter, we are supposed to leave portions of the site in JSP and they will be housed offsite at the contractors location. This is no problem...we just link back and forth to each others site to make it appear...