I don't know if there's anything you can really do to avoid the problem. It may have been a bad board from the beginning. I've been using my XTi in all kinds of conditions for almost a year now and haven't had any problems. It's been in the pouring rain on numerous ocassion and set down in the dirt 100 times. I've never had any problems. I would just chalk your problems up to bad luck and move on. Someone has to get a bad camera every once in a while. This time it was you. Hopefully they fixed it completely and you won't have any more trouble with it.