How close is the light to the computer? Do you have an option to move them to opposite sides of the handlebars? Or mouth the light lower, like on the stem or the head tube?

If there is interference I am guessing the light needs to be very close to the computer to cause it. Even if the light is between the computer and the wheel sensor it should be okay. It's likely that the light is too close to the computer itself.

Another option is to create a Faraday Cage. (It will help disperse rouge electromagnetic signals) Wrap the sides of the light in aluminum foil or a piece of metal window screen (has to be metal, not vinyl). See if that fixes the problem. If it works you can do it carefully so it looks nice. It might not work but it's a very cheap thing to try.