I had a very similar thing happen with a KIA Sportage recently.
Turned out that the lining on one of the rear brake shoes had come
completely loose from the shoe.

Larry A.

On Sat, Oct 17, 2009 at 3:05 PM, C. Chris Snyder
<ccsvanagon@wmconnect.com> wrote:
> Hope some one can shed some light on this new problem with rear brakes????
>
> Yesterday while I was backing out of my drive way, I got halfway down the drive and the vans right rear brakes locked-up. I could not move backwards any further. I then went forwards and tryed again, same thing! so, I tried driving all the way back up my driveway then I tried backing out of my driveway again and low-and-behold, no problems. I drove around and everything was good. No problems after that. The only diffrence I felt was that the brake pedal was and has remained at the top instead of the pedal being about halfway down as is usual.
>
> The master cylinder is right at the max mark..
>
> This is an '87 Wolfburg that has had no brake problems in the past other then over a year ago the brakes all the way around were replaced.
>
> Hope someone can help narrow this down for me.
>
> Thanks in advance.
>
> Chris
>