can I connect mac and pc simultaneously?

[Riccardo]

I recently bought a Mbox 3 pro, and I'm using it connected to a macbook pro (with pro-tools 9) via a 400-800 FW cable, and a pc (just as an external sound card) via a texas instruments firewire pci-e card and a 400-400 FW cable.
I thought I could connect mac and pc simultaneously and switch between them via software or pressing a button, but it seems it's not possible: if the macbook is connected, the card automatically disconnects from the pc.
do you know if there is a solution?

then... a reseller told me not to connect simultaneously mac and pc to the two firewire ports on the mbox because the firewire controller could damage. is that true? if so, what is the second firewire port for?

thank you.

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Riccardo

Macbook Pro i7 2.4Ghz, 8 GB 1333, Snow Leopard 10.6.8
PC i5-750 2.66Ghz, 8 GB 1600, Windows 7 Ultimate 64 bit
Mbox 3 Pro