We have a strange issue with running an Facebook IFrame application (using MVC 2). When I run my app and log into Facebook, I get to the application just fine. But when my coworker does it, she gets the following error:

API Error Code: 100
API Error Description: Invalid parameter
Error Message: Requires valid next URL.

Typically this error is resolved by updating the "New Data Permissions" setting of the Facebook application. However, in this case it doesn't help.

We've also tried logging in with our accounts from different computers and it seems that neither computer nor which one the MVC ASP.NET app is running from matters. The only difference is who is logged into Facebook. We've looked at our Facebook account settings, but couldn't find any obvious differences.

We both have Developer access to the FB application and we both can edit its settings. However, only one of us can actually run the application without getting the above mentioned error message.

Any idea what could be happening here?