I can't say I've seen that error before and I do use Win 500 pretty often with a PSR 500 and 600. I also use the COM Port version where you manually set the port plus I use the other version where WIN 500 searches your com ports for a compatible scanner.
Are you just trying the trial version?
If so, you may want to ask around the forums as the programs author has been missing in action for many months now so there's no way to get the keys to unlock it.
That was the last word I heard in one of the forums here.