I have a 40GB Lacie FW HD, and every now-and-again it "half" unmounts itself.
What I mean by that is, I can be transferring files or the disk can just be sat doing nothing, and (for no reason that I can find) it makes the spin down clunk, illuminating the read/write light. The icon is stuck on the desktop and can only be removed either by turning off the disk or disconnecting the FW cable. Periods between this happening seem to be random, and I have initialised the disk. This happens in OSX.1.5, OSX.2.5 and OS9.2.2, on two different machines.

Any ideas or remedies?