I Have a Verbatim Firelite drive. It worked fine up until today. When I plug it into Win 7 x64 it's not recognized. I can see if on both of my laptops (One running XP, the other Vista).
It's not in disk management or anywhere else.
Install latest chipset drivers. Go into bios and see if your usb is enabled. Use a different usb port. Also hook up any other usb device into your usb, things like usb mice or keyboard or printer and see if windows detects them.
I have seen many people on this forum complaining about Vrebatim external drives. It is highly recommended for you to buy a new external USB drive from a different company and transfer the data to it through the laptop while you can.