>>>>It sure looks like it thinks it is plugged in. You could have a bad charger or battery.
>>>
>>>This laptop is new. After I complained about the previous problems, they sent me a new additional power supply. I'm using the new one now, but I don't think the problem is in it.
>>>
>>>May be I need to re-start again :( I didn't re-start for a week or more...
>>
>>Do you have the old power supply? If so, does it do the same thing with it?
>
>I can put the old power supply back. Basically, sometimes it's not detecting that power supply is on. In this case I change the outlet and last time I changed the power supply to the new one.

You aren't by any chance plugged into an outlet that has low voltage for some reason, or into a UPS that has flakey output?

If you can plug into a different outlet in a different room and get it to charge, suspect the outlet or UPS. Some cheap UPSs put out a square wave AC that your laptop power supply may not like.