Win2k3 Shared Mounted Volumes not working in Vista

I have a mounted volumed on a server that is within a share, however vista
won't let me copy files to it because the drive that the volume is mounted on
is out of space (even though the mounted volume is not)

For example

Server1
--Drive C (Free Space 1GB)
---MyFolder (shared)
----MountedVol1 (Free Space 15 GB)
----MountedVol2 (Free Space 5 GB)


When I'm on vista, and I try to copy a 10 Gig file to
\\server1\MyFolder\MountedVol1 , I get the error there is not enough space
to copy the file, I need to first clear 9 more GB of space.

Is this a known bug? Is there a workaround for this?