I've got 2 of the Cruzer Micro thumb drives (1GB & 4GB) that I've used for a while with my PC laptops. I have a new Macbook and have been unable to get either one of these to mount and be recognized by my Macbook. I've tried both USB ports and both drives... however neither one shows up on the Mac. Other drives have worked, just not these Cruzer Micros... any thoughts or strategies?