T400 Battery Only Will Not Turn On

[pdxpete]

I have a T400 that can turn on only when the AC adapter is plugged in.
With battery only it will not turn on -- tried 2 batteries.
Power manager shows both batteries charging and they do last as usual.

I've noticed a special case where it will turn on using battery only:
1.Turn on power button with AC and battery installed, let windows come up.
2.Remove AC adapter.
3.Shut down windows and when laptop just turns off very quickly turn it on.
For this to work it has to be done within a second or so.

I have windows 7 recently updated, power manager is updated and bios is updated.
The laptop is 2 yrs old and this issue has just started.
I tried these with no luck:
Reset the CMOS backup battery.
Power button "reset" sequence: remove AC and battery, press power
button on/off many times and then hold power button for a minute.

At this point I'm fresh out of ideas.
Any help or ideas would be appreciated.
Pete.

[jayton4]

Do you have ThinkVantage Toolbox or PC Doctor? Run a hardware scan with that. Sounds like something is wrong with the motherboard. Perhaps bad capacitors?