garmin iq3600 hotsync problem

hi - i'm having problems not being able to hotsync. I had previously been able to hotsync but for some reason it would no longer function. I get a message "The connection between your handheld computer and your desktop could not be established. Please check your setup and try again." when i go to setup and check connection i can only get comm 3. i'm not able to choose nor do i get the option to get usb device. i've tried everything my limited experience allows and this is driving me nuts. I know someone out there can solve this problem. thanks