hmmm... the only things I can think of is either:
1. The filter motor is defective. Is it still under warranty? If so, take it back. If not, contact the manufacturer and see if they can do something for you. The number to Marineland Customer Service is 800-322-1266. The one good thing about it is that the thermo safety device is working and it wont catch fire.
2. Lack of cooling air around the filter motor, although this is highly unlikely. Make sure the motor is mounted correctly and not binding the shaft and that there is sufficient clearance for air to flow around it. Also, make sure the impeller isnt binding up from gunk buildup.
Why do I love fish? Because every time I stare into the little world I have created for them, every problem I have just floats away....