Thanks for all the help everyone.
I'm running the latest version of the install disk, it also has a handy configuration program which reads the drive and updates icdfmt.dat with the drive details (although it wipes the drive when it does it).
It's the 3.5inch drive version, running a Seagate 130 Mb drive.
And with how user-friendly it's being at the moment I don't think I'd wish it on an enemy just now.
Unfortunately I've only got the one other wise I'd switch them to make sure it's not a bad unit. It shouldn't be, as the drive can get a certain distance into things before it gets upset, has to be a configuration problem.
I'll keep in mind that you're looking for one though, for when I'm ready to give up. :-)
I'll have another crack at it in daylight, it's 3am and I've honestly had enough for the moment.