hey i have this blackberry 7100g but the problem with it is that i m not getting any network on. this started happening after i changed a theme.

i know its not a problem with my sim or my network provider coz wen i put the sim in another phone it gets full network at the same place.

I ve serached all over the internet and many ppl have this problem but just cant find a solution.
Ive tried updating the software, refreshing the whole data thing but it still doesnt work.

It does get network in b/w for like 2 mins and then its gone again for the whole day.

I really need help man.
thanks