I recall having some issues when I first tried the beta, you had to set it to automatically find the latest drivers and icons from the internet and everything worked fine. I've been doing that since then with no issues over multiple phones, and it even has a nice pic of the imagio in WMDC
IIRC, how to do this is when you get the driver not found error, click on it, and hit change settings, and you should see the option there.
Also, I had another weird issue... the phone would NOT work if I plugged it into my front ports, on a fairly new motherboard, but it works fine when plugged into the back.