its been happening to me too i have to manually go to menu and press retrieve content .. and it still takes a long time to dwnload..but it wrks.. i have the bb curve 8300 dont kno if its da same 4 ur model.
I had this happen when I first got my Berry but it turned out to be a network issue with AT&T. Once they fixed it on their end, my phone worked perfectly. If nothing else works- call your provider and see if it's them.
Posted from my CrackBerry at wapforums.crackberry.com