zoomkat:
I hear that I should attach a capacitor of 0.1u
That sounds like a typical electrolitic capacitor value, which if used across the motor leads, would probably short out when the motor direction is changed.
Now to my mind 0.1uF does not sound like a typical electrolytic capacitor. It sounds like it is non polarised capacitor which should be fine and not stop anything from working.
The fact that you report it does stop the motor from working tends to suggest you have got something else in the description of your system wrong.