Idahomom, there is a fabulous book on visual-spatial learners, which is unfortunately out of print, though every now and then a reasonably-priced used copy appears on amazon (today they're all ridiculously priced). It's Upside Down Brilliance, by Linda Silverman. I got a copy when my dd was tested at the Gifted Development Center, which she runs. Anyway, I remember her book discussing the problem of vision processing issues (visual motor being one kind) in visual-spatial learners - she said it's like being handicapped in your strong suit, or some such thing. In my dd's case, dd very much fit the VSL profile, except that when it came to the block design portion of the WISC, the tester could tell by the way she did the harder problems (she skewed them or something) that there might be a vision problem. They believed she would otherwise have scored better on that section, and they encouraged us to test her again after doing vision therapy. They also noted that the fact that dd wasn't more adept at puzzles was another sign of a vision issue, in light of how strongly they believed her to be a VSL. At the time, it all seemed rather irritating, since not three weeks before dd had had a full checkup with a pediatric opthamologist who had not found any problems (but it was the wrong doc/wrong testing). She has made considerable progress due to the vision therapy; she just finished a 6-month program last week.

Other people are more balanced when it comes to visual-spatial (right brain) vs auditory-sequential (left brain), it's not an all-or-nothing proposition, and where there are weaknesses on one side, the person tends to rely on a comparative strength of the other side to compensate. Ironically, in DD7's case, in spite of the fact that she had great difficulty learning to read phonetically, she is now an excellent speller (according to the teacher, anyway), and I think it's because she has built such a large sight-word vocabulary due to this visual-spatial learning style (combined with the fact that there are so many english words that are exceptions-to-the-rule in terms of phonetics).

Also, on the writing issue, here are a couple articles I happened to come across, in case they might be helpful:
http://www.dukegiftedletter.com/articles/nov7no2_cc.html
http://www.visualspatial.org/Articles/poorhand.pdf

hope this helps; it seems like you may be getting closer to the bottom of the mystery of your son.
smile