Not familiar with this forum's timing, idiosyncracies, etc, so this comment may show up twice.
It appears there is a known solution for this problem, embedded in the latest drivers. I won't try to post the link (that seems to blow up the forum submission sequence) but I found references to the latest drivers at Dell (where I had purchased the system with the problem) and several other locations.
Uninstall and reinstall the video driver, problem goes away.