Zen Vision M is not connecting to computer, tried other cords, other PCs, still nothing?

I have owned this Zen Vision M for 18 months and have been able to use it perfectly on the computer up until recently. Now when I try to connect to the computer through the USB port on the dongle it does not recognize it on the computer, not even for a charge. I checked Device Manager, nothing is showing up when the cord is plugged into the Zen. I know the port and cord works because I plug my Blackberry into it and the Plug and Play feature works for that. The dongle works when charging with the Creative DC adapter that I bought separately. I've spent hours searching forums and it seems no one can pinpoint the problem. Ive tried 3 different computers, Ive tried other cords, ive tried uninstalling and reinstalling the Creative Software. Im stuck. HELP! Please!