Loss of motor control, seizure question.

Tonight while walking the dogs my Australian Shepard suddenly lost motor 
control.  He couldn't stand, kept falling back and to his right while
trying 
to stand.  I told him sit, down.  I don't know if he understood "down" or 
just couldn't do anything else, his eyes were clear but had a kind of
dazed 
"I'm not all together here" look to them.  There was sufficient light to
see 
that his gums were a normal pink.  I started to carry him home until the 
other 2 started to act as if nothing was wrong, so I set the imparred
Aussie 
down and he acted normal.  This was about 15 minutes from the first sign
of 
a problem. We made it back to the house without incident.  Right now he's 
running around having a good time, though staying a little closer to me
than 
normal.  I'll keep a close watch on him throughout tonight and call our
vet 
in the morning.

My question is, has anyone seen or heard of this behavior.  Note that
during 
our walk none of the dogs had a chance to eat or drink anything outside of

my control (which is to say "nothing").

I've also cross posted this to both alt.pets.dogs.aussies and
rec.pets.dogs.