Phone won't charge while switched on.

Hey guys,
I've just started having a problem with my MyTouch 4G in which it won't charge while the phone is switched on. The battery charging symbol displays but the battery % slowly decreases. I have tried using a different battery but no luck. If I go into "battery usage" in settings it says that Wifi & Cellular Idle are the 2 biggest users with 29% each. The strange thing is that these 2 are always using 29% even if I turn Wifi off and put the phone on flight mode. Another user had a similar problem and it turned out to be an app using buttloads of power but I can't identify any on mine doing this. I've done a virus scan. Any ideas?

 

Just did a factory reset and also installed ICS. Got it plugged into a PC and its charged 2% in the last 30 mins. Seems pretty slow but I do realize I'm using a PC to charge and running a hungry ROM, I'll report back how it goes.