First of all, Topic Starter you didnt give us a hint about the error you got. Is the app can not be load? or is it can be load but can not connecting to the internet?
Since you said you already hacking and hacking your phone, i assume you use Opera Mobile or other symbian app (what a wasted of effort if you only use java)
Now let just say you use Opera Mobile, did you use normal Opera or Modification Opera? I ever use an Opera Mod from a friend from Phill, and its integreted with Proxy (usualy to make it faster or free gprs) and Proxy didnt live forever. If the proxy dead then you want be able to connect to the internet using that modification app ^o^ That if the problem is "you can open but you cant connecting"
Iffff you can not open the applications but they are work find before, think again what did you do between its "working" and "not working". Have you ever Hard Formated your phone? If you installed a program in Memory card and you hard formated your phone, the programe will still be there, showing on your menu. But sure it wont able to be load until you uninstall it and re-install it
^o^ for more info you better inbox a Moderator name
Vipul. You will be more confuse here, reading amazing suggestions from amazing people

good luck