Eric,
My first thought would be some debris in the doohickey that locks the blade to the saw. If the lock mechanism worked as it should, even with a blade jammed or friction welded in a cut, it seems like it should jerk your hand and the saw up and down before it ever released the blade.
I would take a real close look at the locking mechanism and look for dirt or crud. Spray some brake-kleen on it and a little shot of oil.
Stuart
