Actually, I just double checked what I had done before. This was on a server using IIS 7. It's not adding a MIME type -- it's under "Request Filtering" in my particular install, there was a list of file extensions that IIS should ignore and ".com" was in that list. I just removed that and it worked for me. Again, not sure if this will resolve your issue or not, but it's worth a shot. Also - you may want to make sure in that all fields in the domain settings are filled out correctly - I have had another experience where something wasn't filled in properly and it didn't give me a warning that it was wrong, but the Save button was disabled. So double check that as well.