I had the same problem. I tried everything, but then turned it upside down for a couple days and put a tiny amount of WD40 on the gear and it unstuck itself. Flipped it back over and it worked. I was also pushing the button too fast i think so the computer portion couldn't keep up with me. I works now, but since I know it is an issue I set the incline when I am not on it.
You can also reset/recalibrate the incline system. With the key inserted in the console, press one of the Incline buttons. While the incline is changing, remove the key. After a few seconds, re-insert the key. The treadmill will automatically
rise to the maximum incline level and then return to the minimum level. This will recalibrate the incline system. This can also help, but I think it maybe just wearing out.
Harwood
December 2009