The stalling happens on my Win7 x64 machine, but oddly enough, does not happen on my Vista x64 machine. Not sure what to tell you on that.
If your Drobo is connected via USB, try connecting it to a different USB port. If it’s connected via Firewire, try connecting it via USB, or vice-versa.
Also try a different/better USB cable. It sounds like there’s some kind of data transfer error happening.