Based on what you have said about there not being any 301 redirects in mojoPortal, I can only conclude that it is not mojoPortal doing the redirect. Maybe there is something installed in IIS like the url rewrite module that is doing the redirect before it ever gets to mojoPortal.
There should be urls for each of your mojoPortal pages in Url Manager. If they are missing then the expected result would be a 404 page not found error. The fact that you are not having a 404 is more evidence that something else is intercepting the requests for these urls before it ever gets to mojoPortal.
Hope it helps,