Well, I succeeded in setting up the cores as you instructed. I did not use the beta but the 5.04 instead. Only thing is, now I have two cores with “Core Download Error” instead of just one! Baffling.
Found this possibility ...
http://foldingforum.org/viewtopic.php?f=4&t=3762
If you are running under Vista there seem to be a few challenges. What a surprise.