A clue here,
my drive just went read-only.
I have the drive on Ubuntu 8.10, it is NTFS, but I’m not sure how I would check the fs without having to reboot in Vista, that is worth a shot. I suspect that the drive became slightly overheated, but doing s filesystem check for NTFS under Ubuntu would be better. It is true that disks will go RO if there is fs corruption, although Ubuntu said it had mounted it RW.
