I ran into this and it turned out to be my Macbook Pro. I hooked the Revo to another laptop (prev OS) and it had no issues detecting the Revo. Once I upgraded the Revo, I could see it even from the Macbook Pro. I've noticed some strange things with the USB on the Mac Pro but keep forgetting long enough to drive me crazy before I give up and try a different computer. I doubt it's the OS version but that's really the only major differences.