I have Bell wireless computers (same model) on both of my bikes. I have a route that I ride near my office at least twice a week, and the computer on my road bike always goes crazy at this one spot after I crest a big hill, speedometer reading 40-50+ MPH and going all over the place. One time I stopped, and the computer just kept going crazy and wouldn't quit. I had to keep riding a little farther before it would correct itself. Next time I rode the road bike, same thing at the same spot, but I just kept going and it corrected itself shortly.
When I rode the same route on my other bike with the same model computer, it never blinked once. And I've had that computer longer on the same battery longer than the one on the road bike.
Any ideas? This is the spot where it happens. Nothing crazy around, just houses and trees: http://goo.gl/maps/3E0Po