Charging problems

I have had my macbook since about October '06 and have recently started having charging issues. The problem started out when it would not charge the battery with the laptop open after the battery would get down to about 70-80%, anything above that it would charge fine. When it is closed it charges fine but as soon as I open it it will stop charging. I then have to close it and unplug the charger from the wall for about 30 seconds then plug it back in with the laptop closed. Once it gets to about 90% charged I can open it and it finishes charging just fine. Open it before 90% it stops charging.

I took it to the Apple store and they said it was the battery because that battery had around 300 cycles on it. So I bought a new battery (37 cycles currently), that didn't work. So I bought a new magsafe, that didn't work either. I have done the battery updater 1.2 and that also didn't help. The problem keeps getting worse, it wont charge while open if it is below about 90%. I am doing the SMC reset as well as calibrating the battery now, so I will see if that helps out.

I am looking for any other assistance, advice, or anything else I can try. Also has anyone else had this problem.

Thanks in advance for any help

****update****

OK, so I have done the SMC reset as well as the calibrating the battery, and to no avail I am still having the same problem. Once the battery gets down to about 85% it will no longer charge with the book open.

Again for some clarification, if I leave the laptop off of the charger and it gets below 85%, once I plug the magsafe back in it will start to charge for about 30 seconds, then it will stop charging and the light on the magsafe will turn off. I then have to unplug the magsafe from the wall for about 30 seconds, close the macbook then plug the magsafe back in. If I try and open the book before it is it hits about 90% it will stop charging again.

Any help or advice will be greatly appreciated....thanks a lot

Batteries + time = death.

This happens to all batteries over time. Replace it.