Some months ago I bought a Seagate FreeAgent usb drive. It turned out that the drive did not play well with linux. After 15 idle minutes it spins down, and closes the usb connection. Later it remounts read-only. After much digging around in the Ubuntu forums I was able to make it work correctly. I don’t even remember what I did. Today I saw a page explaining the problem, and how to fix it, and thought it worth noting.