Why isn't my iPhone 4S charging (apparently) only in some places?
It is possible that there is a problem with the port on the computer, either with the device now being blocked (which is sometimes done via policy in enterprise environments) or the port malfunctioning/disabled altogether. Do other devices, such as flash drives, work if you plug them into the same USB port you were using with your iPhone?

If no devices are working in the port, try the following:

Windows/Mac Desktop/Macbook w/ removeable battery:
1) Shut down the computer
2) Unplug all items from the computer, including power
3) Press and hold down on the power button for ~7 seconds
4) Plug power back in
5) Plug other devices back in
6) Start up and see if the port has started to work again

Macbook without removable battery:

1) Turn off device, unplug all devices except Magsafe charger
2) Hold down left Shift, Control, Option, and Power button at the same time for ~5 sec (note you may see a change in the Magsafe LED color for a second)
3) Power machine on and see if device connects

Sometimes a glitch in the System Management Controller (yes, even on Windows machines) can cause a USB port to go dead. If it continues to not work, reach out to your IT dept./technician to see if perhaps there is a hardware failure.