Blackberrys and XP SP2 don't get along
Support - Protocol Error appears and BlackBerry Desktop Manager closes unexpectedly on a computer running Windows XP Service Pack 2. Heck, folks say going to SP2 should work. I'm sure glad I just have one machine there.
There are certainly issues with it and here's another gotcha. There is a very arcane thing you have to do to solve this but fortunately, there is actually an FAQ on an official Blackberry site (I think this is the first bug I've ever found that had a resolution up there). Here is what you have to do: