I installed a the garage door opener in late summer, early fall. We are now in March and I'm starting to have problems with it. On a few occassions the door will not open completely; it will raise 1foot or so and stop dead in it's track. When I finally get it to move up competely, I try to close if but the door stops 2/3 down (approx. 2ft from the floor) without any apparent reason (e.g. obstruction). I then open the door and it will go up but will only stop when the chain/carrier hits the motor casing. I have adjusted on a few occasion, thinking that it would resolve the proble. It does for a bit but then the problem occurs back again. What can I do?