nokia n73 3g/signal problem

i've recently encountered this problem and i am clueless as to what i should do to fix the problem. My fone has ALWAYS been in dual mode and never had a problem but about a week ago i noticed that whenever i had the 3g icon under my signal bar, i couldn't receive/send texts/calls. Whenever it was just the signal bar, everything worked perfectly. So what i did was changed it to just gsm mode and it has so far solved the problem. Now my question is, is there anyway to fix it so i can still run in dual mode with 3g WITHOUT the signal problems? thanks in advance.