Was that the 1st gen or 2nd gen A&K Masada?
IIRC the first gen was just absolute shit whereas the 2nd gen isn't too bad and compared to the ARES/Magpul PTS version at least it's got a standard V2 gearbox so worst comes to worst just drop in a complete gearbox and you're good to go (ideally you won't have to but it is an option).
For your reading pleasure: http://www.airsoftsociety.com/forums...pinions-44370/
As for your problem I've seen it a few times. It will have to be taken apart to the gearbox however but after it's there you can fix it. It could be the gears have seized, it could also be that a gear tooth broke off and is blocking the gears from spinning therefore causing your motor to pull current from the battery and discharge. When it pulls current the battery pack will heat up as will the motor and because it has nowhere to output that energy in the form of mechanical motion you're left with it all being converted to heat energy.
IMO, if you have warranty then take it back to them and get it fixed, if not then pay a gundoc to look at it or if you're mechanically inclined and have the tools and time to go back and forth for parts then you could do it yourself.