Well, I'm back. Everyone was so helpful, I want to share my experiences and results.
For back-up and downloading, I decided to take a Jobo GigaOne 80 gig. This unit doesn't have a screen for reviewing, but I figured I wouldn't have the batteries, or the time, to do that anyway. I love the unit. It fits in a pocket, and is foolproof and very simple to use. I had three 2gig CF cards, and could download and rotate them in the field if I needed to. The portability and simplicity of the unit (and reliability) were a great advantage.
For batteries and charging, I brought a SunLinq portable 6v solar charger. This unit was light and traveled well, but during the rainy season we had some cloudy days ant a 12v unit would have been good insurance. Also, the charging results were inconsistent (sometimes slow, sometimes fast under the same conditions), and I'm going to test the unit now that I'm home to try to figure out what was going on. I brought three batteries, and that was not too many. I could have one charging and keep two with me while shooting.
I did not bring an adapter for the JOBO so that I could charge it from solar, and I began to run very low. After a great deal of asking and looking around, and some good connections, I managed to find the only power point in about twenty miles for an emergency recharge. In the meantime, I had to stop shooting RAW files for an afternoon to keep my card from filling up. (Larger cards would have given some breathing room).
We talked about the possible effect of high altitude on hard drives, but I didn't notice any. There was a BIG effect on my brain, though, and for a couple of weeks intricate thoughts were....just to intricate! I had only used the the Canon 5D for one week of intensive shooting before going to Tibet, and hadn't mastered all the operations (such as exposure bracketing). This proved to be a challenge when the brain was working on low octane (30% oxygen). Add to that jet-lag, poor food, lack of rest and generally difficult conditions. You could anticipate that anything that you haven't mastered before you ascend will elude you up on the snowy peaks.
Most of my shooting was in monasteries and the lighting conditions were very difficult: virtually no artificial light and precious few windows. The Canon IS lenses were virtually indispensable and preformed amazingly well. Shooting in RAW format seemed essential, too, as jpeg will often "misinterpret" unusual light conditions and produce a distorted image. I sometimes wished I'd brought a mono pod, but generally was happy for the freedom and lack of encumbrance....and weight--equipment gets heavy at high altitude.
Outdoors polaroid filters were the order of the day for rendering the brilliant blue skies, clouds and green hillsides. Lens hoods, too.
Dust was everywhere, indoors and out. I was often shooting quickly and under pressure, and although I tried to change lenses as quickly as possible, I did have some problems with dust, and hadn't brought proper cleaning equipment. That would be on the list next time.
Overall, the trip was magnificent. The Tibetan people are open and full of heart, and being with them was a tremendous pleasure.