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Printers work great by simply activating the OSB devices from the VBOX menu. While in VISTA I can print and use all features of my MAC Snow Leopard printers. When I try to use them under the HOST OS it tells me they aren't available. Simply exiting VISTA (shutdown) works and I can leave VirtualBox running just not VISTA. Any thoughts?

That's the way it works. USB are not shared devices. If you want it to work in both at the same time you don't add a USB filter to the guest but instead share the printer and map it in the guest as a network printer.

Since this has nothing to do with MAC Server as guest, moving to MAC as host.