Reading the various threads around this subject makes it fairly clear that this (a) is not a hardware issue, (b) IS a 'fault' within Streets and Trips, and (c) is beyond users' capacities to 'work around.' I don't know much about writing such applications but it would seem that there is inadequate display buffering to smoothe the transitions from screenshot to screenshot.
Perhaps a 'fix' to this problem should be added to our long Wish List.