Brake shoes are frozen(rusted) to the rear brake drums.  My usual fix is to
release the parking brake, jack up the rear of the van, remove the hubcap,
and whack the lug nut tops squarely with a hammer, the bigger, the better.
When the shoes let go, you'll hear it.  Make sure the wheel spins, let the
van down and go to the other side. Of course, make sure the van is on a level
spot or that the front wheels are blocked.  If you ding up a lug nut, make
sure you adjust it back with a grinder or hammer.  Try your lug wrench on for
size.  Saves a big hassle when you have your next flat!

Tom
'71 Westy, '85 Westy, '91 Carat