Just to update everybody on this, I fixed this over the weekend. The suggestions posted here, plus a suggestion received off-line from Dave Harris, made it possible to fix everything up.

GETTING IN

What I did was remove the 4 hog rings at the base of the seat back (cut them), then started rolling up the upholstery. As I rolled the skin up (imagine taking off a T-shirt), I found 6 more hog rings on the front face which I had to cut. These rings gripped around a plastic rib running along the seam and fastened that seam to a wire molded into the foam cushion. After cutting those free, I was able to roll the skin about 3/4 of the way up the seat.

Sitting in the back seat and looking at the back of the front seat, the recline motor bolts to the inside of the seat frame. Running out of the top is a cable (think "speedometer cable") which arcs up, across the seat back, then arcs down, finally terminating at an enclosed gear cluster at the base of outboard side of the seatback (this gear cluster is where the adjuster knob would be on a manual seat).

THE PROBLEM

According to most, the core problem is that the cable driven by the motor doesn't extend far enough out of its plastic housing; the housing is about 1/4" too long. What happens is that the cable (which is square) works its way out of one side or the other (either the motor or the gear cluster). In my case, it must've worked its way out briefly, then catch again and keep on driving. However, while it was "out", the memory seat sensor (a variable resistor/potentiometer) sensed the motor still moving. Thus, after the cable slipped back in, the memory seat "brain" was stopping travel prematurely.

THE SOLUTION

In the array of responses, I got the following suggestions:

(1) get a new cable with a new design (from Volvo)

(2) drop a part of a nail into the motor drive (Tom Sjodin)

(3) shorten the cable housing by ~1/4" (Dave Harris and others)

I chose #3.

To do this, I:

(1) Removed the two bolts on the top of the drive motor. These hold a plate, which in turn holds the drive cable on to the motor. I believe these were 8mm.

(2) Pull the motor side of the cable free from the motor.

(3) Using a small flame (e.g., a butane BBQ grill lighter), heat up the metal on the plastic cable housing for approx. 10-15 seconds. Gently (but quickly) use a pliers to pull off the metal end (the metal WILL be HOT!).

(4) Use something to cut off about 1/4" of the plastic cable housing. I used a stripper I have for cutting coaxial cable, but could just as easily have used a nice, sharp X-acto or utility knife.

(5) Heat up the metal end you removed in step #3 (tip 1: I found that letting the flame go inside got the most important part heated up quickly) and quickly push it back onto the plastic cable housing. Make sure you push it all the way onto the housing. (tip 2: I found that holding the cable with a spark plug boot puller worked well, and using the female side of a 1/4" ratchet drive extension to push on the end of the metal end).

(6) Reassembly is the reverse of the removal. The only potential difficulty is in making sure that the cable is rotated correctly to fit into the motor's drive mechanism. Also, I stuffed a little more grease into the metal end to replace the little bit that burned off during the two heat-up phases.

OTHER NOTES

In my case there was a step (0), in which I used the electric controls to move the seatback as far forward in its travel as the memory seat computer would allow, and step (5a) in which I chucked the square cable into a cordless drill and moved the seatback all the way physically forward as the gear mechanisms will allow. In doing these two steps, I basically recalibrated the seat's sensors, avoiding a trip to the dealer for computer-based recalibration.

I tried to use hog rings on reattachment of the seatback, but got frustrated b/c I had an ill-suited pair of pliers and too-heavy gauge hog rings. If you're going to use these, seek out a genuine upholstery supplier to buy these tools, as the stuff I purchased at the hardware store was useless. Fortunately, I used the venerable ZIP TIE (in true MacGyver fashion) to act in place of hog rings. These worked very well, and required no special tools. The only place they'd be remotely visible is in reattaching at the bottom, and using the partially translucent white zip ties made that mostly invisible unless you're looking around under the seat (of course, the original hog rings were bright silver and plainly visible).

Phew! That was a long one. I'm sure I left something out, so don't hesitate to ask. Thanks again to all who replied, and esp. to Dave Harris and Tom Sjodin who volunteered their phone numbers so I could bother them over the weekend :-)