Sounds like the "engineer" at this "studio" was either having a bad day or didn't know how to set up his system. There is no reason using an SPDIF device should have crashed his PC.
With the mbox it isn't SPDIF or USB- you MUST use USB because that's the only way the mbox gets sound into and out of the computer.
There are 2 ways to get audio into and out of the mbox. Analog and SPDIF. Analog is stuff like mics, synths plugged into the line inputs, etc.
S/PDIF (Sony/Phillips Digital Interface) is a way of getting digital audio into and out of the mbox, and a great many other audio devices. If you don't have a preamp or effects device that has SPDIF I/O then don't worry about it.
C