>>When I had those situations, I removed the battery completed and put it back on after. Sometimes, this may reset something. Also, I also faced a situation where I had to remove one small card, from the back of the laptop, for a global reset. In both cases, something was stucked which was avoiding the contact to be done with the AC adapter.
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>Thanks, I will try that.

What make and model is the laptop? Not that I know everything about all of them, but that might help with others who reply.

We had a batch of HP 5000 or 5500 here one time that had a problem with a spring that was in the battery compartment. This spring stopped the battery from charging good and also kept it dead when unplugged at times. The fix was actually to rip out the spring. In our case HP also replaced all the batteries that were damaged by the problem. But, that was when the laptop was under warranty.

Also try plugging in the laptop without the battery in at all.