My Metro500 interfered with my Cateye Strada. After a little trial and error, I now have the light mounted underneath my handlebar and no longer have a problem. As it turns out, I like having the light a bit more hidden in this manner. I just bought a Polar M450 but have only had a chance to use it once. I have it on my road bike with a Dart200 light, and had no issues. I haven't tried it yet on the bike with the Metro500.

As an additional note, I had the Sigma, same model as yours, and always had interference problems with it. Maybe it's been fixed with a newer generation. It's resting in a baggie in the bottom of my parts bin.