I've never used c:geo, but I looked quickly at their website.
Given that the app does its' own networking, and doesn't require a browser to fetch stuff, it seems hard to believe that there is a reason why it would work on the OTA2.1 and not on Ivanmmj's "Official 1.0". Those two ROMs are essentially identical, with the exception of one or two root tools which are highly unlikely to be in play here.
I would check other things first
- network connectivity?
- do you see traffic on your wifi router if you use the app when you have WiFi on?
- temporary problem on the c:geo server side?
- clear the app cache and data areas, uninstall and reinstall?
If there is some mysterious dependency on other system software components, the only way you will discover that is to set up the Android SDK on a machine, fire up ddms, and turn on Verbose logging, and then watch for any errors to be reported when you invoke the application.
(If you are not tech-savvy, I wouldn't attempt the latter - I would just give up instead.)
eu1