If you are using an external power supply, you should not connect the +5 volts to Pin 1 of the USB connector.
Not sure if you meant that in post #1 USB connections.

If you do, it will cause an over current condition, and the USB port will shut-down.

The capacitor should be at least .22uF (220nF).
It may still work with 100nF, but it may also be unstable.