Sounds to me like you have a wiring problem...either behind the control panel (assuming the switches for all 4 slides and jacks are next to each other) or in the mechanical compartment below.
When we picked up our MH (2004, we got it in June 2010), the dealer was having trouble with the slide. They replaced the solenoid that controlled the movement, and called it fixed. A few weeks later (on the road, of course) it started refusing to retract just like at the dealer.
I went down and looked at the shiny new solenoid, trying see if it 'burned out' again. There was a wire running from one of the hydraulic pump's switches (sensors? not sure what it really is) that had a junction it; it was a disconnect. Well, I jiggled that junction, and low and behold the slide worked great again.
A week or two later, same symptom, and again nudging the junction seemed to fix it. So, I found a way to orient the wire so that the junction wasn't swinging out in space, and haven't any problems since.