Well, Timex sucks. They have issues with their heart rate monitor signals, and they won't admit it, nor will they address the issues with their "upgrades". I have a lot of Timex, and I've dealt with them regularly until I got too frustrated to care anymore. I'm taking the loss and writing it off at tax time.
The best thing you can do is find a good, reliable company that has better monitors that actually work, and when they don't, they will address the issue and/or replace the watch.
(sorry... bitter).
Koffee