SFU was a tad cryptic so I gave up! I ended up using a linux box to NFS mount to the XServe then serve the same directory using it's own samba server. Clunky but it worked..... and fast too!

Anyways, it turns out the Samba performance problem was masking a fundamental issue with Windows Quicktime which resulted in segmented .dv files with a .mov wrapper not opening, the macs open them no problems...... So they've agreed to replace the windows machines with macs instead. Happy days!!!!