I doubt that would have caused it, but I could be wrong, if it spun up fine at first, and didn't bind and hum, I would have to say it wasn't teh seal since it would take a lot more binding and friction to break the motor.
Almost sounds like you may have lost some brushes and it's no longer energizing the windings.
I'm thinking for what it's worth to open it up again and inspect it before buying a new one.