Card reader/writer and "write cache enabled" in Win2k

I have a Zio multicard reader/writer, USB 2.0, on my computer running
Win2k, SP4.

I've always just used the thing in the "normal" way of transferring
image files from the card (Smartmedia) to the PC, and it's worked
fine, of course. Today I tried copying some pictures from the PC to
the card in the reader (I was going to take the card to a self-service
printing kiosk) and I swore I'd blown the thing up. I got a bunch of
errors accusing me of trying to disconnect the device without stopping
it (not true - the card was in the reader, and the reader remained
plugged in, I just got the errors the moment I dragged a file from the
PC to the reader/writer).

A friend suggested I try disabling the "write cache enabled" for the
card reader. But when I right click on its properties and go to the
middle tab, "write cache enabled" is grayed out (it's also not
checked, so I don't even thing write cache IS enabled, whatever it
is).

So is this the correct path to go? And why can't I copy files from
the PC to the card in the reader? Yes, the drivers are current, taken
from the manufacturer's web site.