I just got a new flash drive and it worked fine on my iMac yesterday, and now suddenly it no longer appears on the Desktop or anywhere else on the computer that I can find. But when I pulled it out of the USB drive, it said the device was not removed properly, so it must have recognized something was connected. How do I access the USB drive? Why is it no longer showing up on the Desktop? I tried plugging it into different USB ports, I restarted the computer, nothing works!