After I change my bandsaw blade, I ran a piece of MDF through it as a test, and it was fine. Then I tried to do it again, and the blade didn`t move, although the motor was humming. Then the breaker tripped. So I took off the auxiliary table, then opened up the bandsaw looking for the problem. Nothing seemed to be amiss, so I tried to run the saw again, and it ran. Put the saw back together, tried to run it, and it froze. In a burst of brilliant inspiration, I turned the motor pulley half a turn, and the motor ran, allowing me to saw some slices off 5" thick oak. However, every time I stopped the blade or at least two out of three times, the saw wouldn't move until I turned the motor manually.

Any idea what may be wrong, and is this likely to be an expensive repair or replacement?

Thanks.