If you post about a problem and later solve it, you will help many people in the future if you summarize the problem and (very important) the fix. In this case, Nelson H. F. Beebe installing DragonFlyBSD 5.6.2 on his Dell Precision 7920 workstation.
A running description of activity related to DragonFly BSD.
Not much of a fix though – work around more like.
The part I am happy about is that someone followed up with a coherent, complete answer on what they did.