How can I fix my ProForm 530i treadmill?

I have a 4 yr old ProForm 530i treadmill (2.65 HP motor) that recently has stopped running. The console seems to work properly and the incline as well, but when I set the speed to any non-zero value, the motor starts off very fast and then stops about 3 sec later. I removed the cover and ran it, and noticed that the commutator on the motor arcs quite a bit for those 3 sec. I put the console into debug mode to get more information, but wasn't able to ascertain much. The controller status value starts at 0 (off) then goes to a somewhat random (and undefined value such as 9, 192, or 12 for a moment, then to 1, which is supposed to indicate reset. I don't know if this means that the unit reset it due to current limiting or something, but I never get any error codes. I am presuming that the motor is bad, but I am unsure if this is truly the culprit, not having ever repaired a treadmill. The last month the belt has been slipping a bit, so I did recently tighten the belt slightly (1/4 turn on each side as suggested), but I have not lubricated it in some time. During my testing, I also reduced the tension on the belt so the motor was no longer driving it, but it still only runs for about 3 sec before shutting down. Does anyone have any thoughts on this? It has been very good these last 4 years, 1447 miles and 40 pounds.