I just had a similar problem. Somehow the report (frx) file got corrupted. (I build all my reports into the exe.) When I looked at it in the development environment, when I tried to modify the report, I got an error: report has circular reference. (This report has not been modified in the last 6months.)

So, I restored the report from backup and built the app again.

Voila, report shows.

HTH,
Mike