Solution that worked for me
"Seems that the driver didn't automagically install the first time I plugged the phone in."
Phone: Nexus S 4G
Computer Make: Asus
Model: UL30A Series
Type: 64-bit Operating system
OS: Windows 7, SP1
1. When I plugged in the USB to my computer, the phone would charge, and the notification bar would briefly show the USB icon and then it would disappear.
2. Phone didn't prompt me to turn on USB storage, but I could turn on tethering and would have network access. The phone did not appear as a storage device on my PC.
3. I plugged it into another laptop and it worked perfectly.
4. Plugged it back into my PC, tried all the different USB ports with no luck.
5. Checked Start > Devices & Printers. The Nexus S appeared as a generic device at the bottom. Right click icon and select "Properties" and the info was mostly greyed out. Select "Hardware" tab and then "Properties".
6. In new Properties window, selected "Driver" and then "Update Driver" and then "Search automatically..."
7. It found the driver, updated, and then the phone's USB storage mounted correctly. Seems that the driver didn't automagically install the first time I plugged the phone in.