Did you recently run an update? I know that some 880's had a problem after an update. Remove the battery completely for 30 seconds and insert it back.
In answer to your original question, my tilt sensor did fail after about 1 year. It simply would not wake up the remote at all. I was positive it had nothing to do with an update since I didn't update my remote for over 6 months. I ended up returning it within the warranty and have not had a problem with my new 880.