According to M-Audio they do not recommend Hot-Plugging their devices.

Reports have come to our attention of isolated problems when hot-plugging IEEE 1394 (aka “FireWire”) devices. (Hot-plugging refers to making 1394/FireWire connections when one or more of the devices—including the computer—is on.)

When hot-plugging, there are rare occurrences where either the FireWire peripheral or the FireWire port on the host computer is rendered permanently inoperable. While M-Audio products adhere rigidly to the FireWire industry standard and pass stringent internal testing, the possibility remains that hot-plugging your M-Audio FireWire interface with some computers may result in the type of problem described here.

We strongly encourage you to protect your equipment by refraining from hot-plugging any bus-powered FireWire device, including the M-Audio family of FireWire products. Connect your FireWire device while both the computer and FireWire device are powered off. Power on the FireWire device, then turn the computer on last. If you are using bus power (systems with IEEE1394 6-pin connectors) make sure you make the cable connection first, then turn the FireWire device power switch on, and turn the computer system on last.

M-Audio is being proactive in investigating any issues that may adversely affect their customers. Please consult the Knowledge Base in their Support section at m-audio.com for updates on this important issue.