I'm just thinking out loud about this, but something doesn't seem right with this situation Steven. Questions that come to mind are: Why is it only on those windows when your product and process were identical for the entire house? Did the contractor contact you the day he noticed it (the day after you completed the job), or did it take him 2 weeks to contact you? I've never used Blue Voodoo, but I don't see how the contractor could not remove soap residue no matter what he tried.
In my opinion, something isn't adding up. I would ask some questions about any other work that was done to that section of the home like the staining/sealing or dayseven work completed before you did the job. Was a clear sealer sprayed on anything in that area?