rickwellman,
Where is the "click" you hear coming from? The slide out controller (relay clicking, gentle click) or the slide motor/gear box (gears slipping, solid clunk)? How many slides do you have on the rig?
If it's the slideout controller, inspect power & ground wires going to the controller. Especially the ground. Two years into ownership of our GBM (we bought it new) I discovered the ground for the slideout controller was never adequately fastened. Also, the power wires leading to the slide motor(s) should be inspected. Disconnect and reconnect them firmly.
If it's the same slideout motor as mine, the front facing mounting bolts on the motor (three of them) may loosen, or a boss they screw into breaks. Then the motor is allowed to twist a bit while engaging and moves out of alignment with the gear train. Yup, had that problem too.
For what it's worth, the slide controller on our Cruise Master WILL NOT allow the slide to go out while the engine is running. However, it will allow you to bring the slide in with the engine running, which is usually what I do to give the slide motor a few extra volts to play with.
Good Luck,
~Rick