-When you run your program and probe the motor output value, is it a "0" or is it grayed out? If it's grayed out that means that portion of your code isn't running. If you have any other speed controllers or relays are they indicating they are receiving a signal?
-With some PWM cables it is necessary to shave off a piece of plastic from a PWM male end. This is only for the PWM cables that have a piece of plastic sticking out of the main connector housing. You can (kind of) see an example here:
http://www.vexrobotics.com/products/...re-cables.html
Any other normal PWM cable should not require any modification to be plugged in. If just one is giving me trouble I usually pull it out and make sure that the pins are absolutely straight and re-insert. Take every precaution necessary to ensure you do not short the 5V line to Ground and that the robot can not hurt anyone if it starts running. The most efficient way to do this is to disable your robot, fix your connection, stand back and re-enable. When installing in a Victor, make sure that the orientation is correct (B for Black/Brown == Ground) and it should be pushed in all the way.
Once they are working correctly, we like to hot-glue them in place. This holds them in place and if you must take them out hot-glue is fairly easy to remove. Again, be careful to not melt any wires!