Presario 700 Battery Charging Problem

I recently bought a new battery and followed the recommended procedure
of fully charging and discharging it several times. It worked great
for a month but now I sometimes have difficulty getting it to
completely charge up. (Other times it'll charge all the way to 100%.)

When I open Power Meter from the taskbar, I can see that I'm on AC
Power and the amount of the battery charge. I unplug the charger and
Power Meter shows that I'm now on batteries. Then if I plug it in
again, it says "Charging" and the total battery power remaining will
go up one or two percent. Then the word charging will dissapear and
the battery will remain at whatever % charge it's at.

Does this indicate a defective battery or something defective in my
computer?