Hi Jason,
Many thanks for the beers! Much appreciated.
The first thing is to find out what the error is, I have some notes here about how to do that:
http://www.mojoportal.com/basic-troubleshooting.aspx
But, I can say I think it is probably a conflict between the mojoPortal Web.config file in the root vs whatever application is running in the /secure folder. These can usually be mitigated as described in the article linked here:
http://www.mojoportal.com/developer-faq.aspx
However, mojoPortal also has files in the /Secure folder and it may not be possible to resolve all issues in this case, I'm just not sure, depends what the conflicts are.
Hope it helps,
Joe