If you can operate the rear windows from the drivers switches, but not from the rear switches, then its probably the lockout switch (the o - switch thats sideways on the drivers switch panel) that others have described. One setting turns off the rear controls to the rear windows, so back seat passengers can't operate them, only the driver can. The other setting makes them all operable, and I have no idea which setting is which.

If you can't operate the rear windows from anywhere, which is what I think you're describing, than the problem lies somewhere else. Unfortunately, I don't have my car or my Bentley to look at for comparison, so I really can't offer you much advice right now. I'll check my fuse panel for you when I get the chance, or maybe someone else can take a quick look and confirm that you have the wires on correctly.

I would start by cleaning all of the switches really well and see if that helps.
(there is some info in the FAQ: http://brickboard.com/FAQ/700-900/BodyGlass.htm and http://brickboard.com/FAQ/700-900/ElectricalCircuitsRelays.htm#Power_Window_Switches)

BTW, windows came from a '93, if that makes any difference. Hope you get things figured out!