Similar thing happened to me when I drove way up north (Flin Flon, MB) last summer. Before I left, everything was fine. We stopped a few times along the way, no problems with the battery. When we got to our destination everything seemed fine until we went to start the car and we got nothing. Very odd, because it was like night and day, good battery, dead battery. When you got in the car, the lights came on, everything worked until you went to start then it would all just die. Jumpstarting worked fine, but as soon as you turned it off, it would be dead again. Turns out the battery had a bulge on one of the sides and was toast. It was the original factory battery and was 6 years old so no biggie really. Luckily there's a Canadian Tire up there and I was able to buy a new one.
Another issue I had once was a corroded ground caused some funky issues with the cluster and interior lights (background lighting flickering, cluster throwing all kinds of warning lights randomly, clock & trip odo resetting while you're driving...). I cleaned the grounds under the battery, and the 3 under the driver's side dash, but the problematic one was the ground just beside the driver's footrest. Once I cleaned that up everything was fine. I also added a generous glob of dielectric grease to each one so it wouldn't happen again. In fact that's good advice for any electrical connector on these cars. If you unplug it, pack some dielectric grease in there. That's fixed a lot of people's problems with the MAF on the ALH motors.
So yeah take your battery down to an autoparts store and get it checked out, and if it's ok, check your grounds (FYI all ground wires on VW are brown, and a Haynes/Bentley manual would help you locate them).
Hope that helps!