Something I forgot to mention... Important(not sure)... I am using XP not Vista.
I remember the first time I plugged in my BB after installing DM, there was some activity going on in the windows systray(lower right screen). During this activity, I believe it was installing drivers and such.
It truly sounds like your having either driver issues or usb issues. I know you mentioned above "The ports are working". But you never really said if you are using a usb hub.