What is your Computer's OS? Is it Windows? Windows 7 or 8? I have a desktop with Windows 7 and no problems connecting my phone to my desktop. However, my laptop, which has Windows 8, will not see my phone when I have connected the two. Strange.
You need to enable Mass Storage mode if you want to transfer files. It is in the System options. It should be an option in your notification bar when you connect to your PC with an USB cable.
I have the same problem, but with WindowsXP Pro.
I escalated it to Tier 2 at Verizon and the response was it is not our problem, go to Motorola.
May have to return the phone.