incorrect charge reporting & power button

[pabloboloman]

Hi!, some time ago I was using my Focus and suddenly the power button stop working, it was weird because later the phone turns off, so I ended up plugging in the charger and for my surprise the phone was with 0% of battery, but before it said that it was like 90% (the phone was actually uncharged)..anyway, after that everything went back to normal...today I had the same issue..button not responding..turn off with 95% of charge (incorrect), charge, OK..I've been reading some forums and other people have had this issue...anyone knows the final answer to this? it's a batery problem? an SO problem? hardware? most of the time all works fine..

thanks in advance