The roller bearings should be lubricated with a light oil or silicone spray. The hinges on the door can also use silicone spray. Don't lubricate the tracks and don't use grease on anything other than the rail for the trolley to slide. The rollers should roll not slide. If you have a chain drive do not lubricate the chain. Doesn't need it.

Thanks Don.

Kind of what I was thinking, but I wanted to hear from someone who wasn't guessing!

"silicone spray" is not a suitable lubricant for bearings of any type.

brickeye you might be interested in this.

http://www.nmbtc.com/pdf/engineering/bearing_importance_of_lubrication.pdf