OS/2 guest cannot write to floppy disk

[Julien Pierre]

I am using a Vista x64 SP2 host, and OS/2 ACP2 guest. When I mount the floppy drive in the guest, I can read files from the floppy just fine. But I can't do any writes. All writes (such as COPY, DEL, etc) result in a SYS0039 "The A: device is not ready".

The floppy drive works fine in the host, and I am able to do those same operations in the host OS to the same floppy disk just fine (if I unmount the floppy from the guest, of course).