Well, I downloaded and tried both DR680 v110 files - the US one, and the one from the Euro site, DR-680 connected to my XP laptop this time. They appeared the same as they do on my Vista machine, and the results were the same, too, each producing it's own error code, as noted before. The US file is a .zip.tgz, the Euro one has just a '.zip' tag. The US file is almost 200KB larger - 783KB vs 573KB. Weird.
The only consistent thing here, no matter which way I try it, is that the machine refuses the update.
Any other ideas?