I just found this thread and would LOVE to solve this issue also. I have the same problem on my campus' network with fring. I have also tried the uninstall and reinstall. Weird thing is, I get the same thing for AIM on my iPhone (also tried the uninstall/reinstall). I can get both fring and AIM to login under Edge, but as soon as I switch to WIFI, nothing, fring times out, and AIM says "I need a network connection...."
To top it off, AIM, Skype and all sorts of things work FINE when using my Macbook Pro on the same wireless network. It really seems to be localized to my iPhone, but plenty of apps work fine using the WIFI on the phone too (Safari, Shazam, etc).
Are there specific ports that fring needs to login? I have also searched all over and can't find any good specific info on what fring is really "doing" on the connection side.
Anything would be awesome!