Raina,
You wrote:
>  Her horse -- an 11 year old, recently gelded (1 year ago) Polish Arab, 
>will *not* lead on the trail.  He will follow other
> horses through, over, or around anything but if he is put in front of
> another horse he simply stops.  He doesn't appear afraid, or try to turn
> around, he simply doesn't move forward, or after much encouragement he will
> walk, but only a few strides before he stops again. 
My new gelding was like this last fall.  We'd joke that no matter how 
fast he was, he'd never finish better than second!!
>          On our last ride, we tried to have him lead for a little while and
> then just as his rider felt like he was about to stop, she would ask him to
> "whoa" and then praise him and try to go forward again.  If he did a stretch
> of trail well (this happened primarily on the way home) she would stop him
> and let my mare lead for awhile, then we would switch back.  These methods
> were tried with and after traditional methods (leg aids, crop, tree branches
> etc -- which did not help at all).  
By asking for a stop when she sensed he was stopping, was she 
inadvertantly rewarding his behavior?  (ie. it is ok to stop here 
since you feel like you may want to?)  We asked the horse for a few 
more steps, or kept motion but had another horse pass & continue.  We 
found distraction helped - leg yields, bending, anything to put his 
mind back on us.
You didn't mention how long the horse has been on the trail - is this 
a new experience for him?  I found that Rocket did improve over a 
LONG period of time.  It's been a little over a year now, & he's is 
FINALLY deciding that not only is it ok to be in front, he WANTS to 
be in front!  He actually raced for the last 2 finish lines!  
(Admittedly, it is a far cry form top ten yet - not much difference 
between 55th place & 57th out 112, but it's the attitude that counts.)
Sometimes horses seem fascinated by new objects and stare into the 
distance.  Get their mind on the work at hand.  Other times, the 
horse is intimidated by the partner's horse who is higher on the 
social pecking order.  The aggressive/submissive signs may be quite 
subtle but very real to the 2 participants.  ("Don't youe DARE pass 
me or ELSE! or You're in front - get back where you BELONG!)  It may 
help to ride with severl more riders to see if it makes a difference. 
***Also remember that he is learning social behavior if he is going from 
being a stallion in an isolated turn out paddock to part of a gelding
herd!!!!***
Be prepared to spend a little extra time w/ your riding partner & 
her horse.  There may need to be quite a few training sessions before 
serious miles can be covered on conditioning rides.  It took Rocket 
4-5 months to even consider stepping in front of Major.  He was 
praised WHILE he was leading (never when standing still).  He was 
ridden in large groups (saddle club of 75-80 riders), small groups 
(4-5 riders), in pairs, and by himself.  As he gained confidence, he 
did better.
Who knows, he may be first one day after all!  Don't give up.  Be 
patient!  Only reward good behavior AS HE PERFORMS IT!  (not 
afterwards.)
Linda Flemmer 
ABF Challenger ("Rocket") & Eternal Point ("Major")
Blue Wolf Equestrian Supplies/ Blue Wolf Ranch
Chesapeake, VA
   "In case of emergency - Fur side up, steel side down!"