The website http://wiki.xensource.com/xenwiki/VTdHowTo indicates that the X48 chipset should have support for VT-d. Can you please confirm that VT-d support is fully available on the C2SBX+ mainboard and therefore support virtualization?
We do support virtualization with this mainboard. Make sure to have latest Bios installed from our website first. You need to enable virtualization support in the BIOS at Advanced-> Advanced processor options-> "Intel virtualization"
Also VT-d option can be enabled at the “Advanced” section. The default setting is disabled.