MacBook won't charge on AC, MagSafe light dim & green only

Question

Hello all,
I'm hoping that someone might be able to help. My MacBook refuses to charge its battery! It sounds like a few people have similar problems.
The AC adaptor is NOT the problem - or at least, not the fundamental problem, since I just swapped mine for the known-good one from my sister's almost identical (and week-old) MacBook, and I get the same symptoms.
The symptoms are that the MacBook allows being powered from the AC adaptor, but in the battery menu bar item it simply says "Battery not charging". The AC adaptor's light is green, but extremely dim. It should be orange, since the battery is not full.
Sometimes it does charge, and I haven't been able to figure out why it does so at these times. Even then, the AC adaptor's light doesn't come fully on, staying dim and green while it's charging the machine.
I've reset the power management unit by pressing the power button while no battery or AC adaptor is connected, followed all the steps in Troubleshooting MagSafe adapters (Ts1713) including checking the MagSafe connector for dust and broken pins, reset the pins on the connectors, swapped the trailing cord on the AC adaptor, and restarted my MacBook many times!
I'm running 10.5.4, so I should have Battery Update 1.2 installed but I've never run it.
Also, if I take the battery out completely and run the MacBook just off the AC adaptor, the green light on the AC adaptor is still very dim. The system recognises that there's no battery but I don't get the strong green light that I should get.
Do I have a hardware problem, and if so is it with the battery or the MacBook?
I don't have another battery to test with right now and I can't get to an Apple dealer.
Below is the Apple System Profiler output for the Power section.
Many thanks in advance for your help.
Battery Information:
Model Information:
Serial Number: DP-ASMB013-358e-7e58
Manufacturer: DP
Device name: ASMB013
Pack Lot Code: 0001
PCB Lot Code: 0000
Firmware Version: 0102
Hardware Revision: 0300
Cell Revision: 0100
Charge Information:
Charge remaining (mAh): 1130
Fully charged: No
Charging: No
Full charge capacity (mAh): 5279
Health Information:
Cycle count: 286
Condition: Good
Battery Installed: Yes
Amperage (mA): 0
Voltage (mV): 11206
System Power Settings:
AC Power:
System Sleep Timer (Minutes): 10
Disk Sleep Timer (Minutes): 10
Display Sleep Timer (Minutes): 10
Automatic Restart On Power Loss: No
Wake On AC Change: No
Wake On Clamshell Open: Yes
Wake On LAN: Yes
Display Sleep Uses Dim: Yes
Battery Power:
System Sleep Timer (Minutes): 5
Disk Sleep Timer (Minutes): 10
Display Sleep Timer (Minutes): 1
Wake On AC Change: No
Wake On Clamshell Open: Yes
Display Sleep Uses Dim: Yes
Reduce Brightness: Yes
Hardware Configuration:
UPS Installed: No
AC Charger Information:
Connected: Yes
Charging: No

Answer 1

My computer starting having the same problem tonight. My battery is only at 52 charge cycles...
Battery Information:
Model Information:
Serial Number: DP-ASMB016-3765-69a
Manufacturer: DP
Device name: ASMB016
Pack Lot Code: 0002
PCB Lot Code: 0000
Firmware Version: 0110
Hardware Revision: 0500
Cell Revision: 0102
Charge Information:
Charge remaining (mAh): 4618
Fully charged: No
Charging: No
Full charge capacity (mAh): 5211
Health Information:
Cycle count: 52
Condition: Good
Battery Installed: Yes
Amperage (mA): 0
Voltage (mV): 12244
System Power Settings:
AC Power:
System Sleep Timer (Minutes): 0
Disk Sleep Timer (Minutes): 0
Display Sleep Timer (Minutes): 60
Automatic Restart On Power Loss: No
Wake On AC Change: No
Wake On Clamshell Open: Yes
Wake On LAN: No
Display Sleep Uses Dim: Yes
Battery Power:
System Sleep Timer (Minutes): 0
Disk Sleep Timer (Minutes): 0
Display Sleep Timer (Minutes): 0
Wake On AC Change: No
Wake On Clamshell Open: Yes
Display Sleep Uses Dim: Yes
Reduce Brightness: Yes
Hardware Configuration:
UPS Installed: No
AC Charger Information:
Connected: Yes
Charging: No
Does anyone have any idea on how to fix this?