I have had a Sonnet Allegro USB 3 card installed in my mac pro 3,1 for some time but have rarely used it except infrequently with a Compact Flash card reader so I didn't notice a problem. However I jut bought a 4TB USB3 external disk & discovered that when it is powered up that I get all sorts of erratic behaviour with my Magic Mouse. It's very laggy & sometimes just stops responding. If I power off the external disk the problem goes away. I have now tested with a couple of other USB3 devices (external disk docks) & exactly the same problem occurs when they are powered up. I did some Googling & found references to others seeing similar behaviour with USB3 cards in the Mac Pro. I am running Mountain Lion 10.8.2 & the latest Sonnet Allegro drivers (1.0.8b). Is there anyone running the same card without problems with a Magic Mouse or conversely can anyone recommend a USB3 card that does not interfere with the Magic Mouse? I had been considering saving a PCIe slot by buying the CalDigit FASTA-6GU3 combined USB3 & 6G eSATA card but would like to be certain that I won't encounter the same problem.