5kcs brakes dragging

[Steve Sherman <steves@cyrix.com>]

An unusual thing happened to my wife's 86 5KTW today.  About 2-3 miles
from home, they noticed a smell like burning brakes.  It was pretty
strong so they walked back home...

Later I went to retrieve the car, and checked it out.  Nothing terribly
wrong, other than the lingering smell of hot brakes.  I drove it home
slowly, and checked for the obvious.  Parking brakes releasing (at least
enough to start rolling on a downhill grade when I let off the pb). 
After a mile the disks seemed hot considering the way was mostly flat
and only the one stop from 30mph.  Not too hot to touch, but you would
not want to leave your hand on them for long.  Tried turning off ABS in
case it was somehow screwing things up, but that made no difference. 
All the wheels seemed equally hot, so no one wheel or axle was sticking.

There wasn't any noticible drag on the car, at least not noticible at
the low speed I was going (~30mph).  It could coast ok, and would roll
downhill.

At home the disk were hotter, not "glowing", but too hot to touch for
long.  Calipers were warm but not hot.  I did not get the overpwoering
hot brake smell that my wife got earlier, but I was only going
2--30mph...

For comparison, I ran the route with my 5K, and my disk and rotors were
cool after the same trip... So there is definitely some drag on the 86
5K's brakes.

Seems to me that the only thing that could be affecting all 4 wheels
would be the master cylinder.  Does that wound right?  Any other likely
culprits?

BTW - about 2-3 weeks ago I had a shop replace the rear pads and rotors
(since I usually don't work on brakes).  Seems unlikely, but any chance
that they might have done something to cause this?

TIA

Steve