Are you and the OP one in the same or are you just experiencing the same issue?
Try following these steps: What to do next if Jl Cmder will not connect and wipe - BlackBerryFAQ
Also, make sure you're not using a USB hub or extension cable. Plug the USB cord to a rear USB port. Try multiple ports. If still no luck, try rebooting your PC or try another PC altogether if at all possible.