Hi, I'm not too sure if you have experienced this before, but any advice or links to the right direction is much appreciated

iPhone Generation : 3GS
Unlocked? (or Part Number): Artifically unlocked (Part Number MC145C)
Current Firmware : 3.1.2
Current network: Maxis
iTunes Version : 9.0
PC/MAC : Mac
Jailbreaking software : blackra1n
Problem Encountered : I keep getting a 'Could not Activate Cellular Data Network' message whenever I try to either send MMS or use 3G
Steps Taken So Far :
1) Checked the settings for MMS in this thread (http://forum.lowyat.net/topic/868281/+10) and mine is the same details
2) Resetting the phone. Didn't work. Still got the same message.

Other Information/Remarks :
I'm wondering if it's the network itself is having problems, or it's my own phone. This has only happened recently (the past few days). Previously, I haven't had this problem after enabling MMS.Any advice is appreciated!