Sometimes, when I use a FireWire based PowerCore alongside a Firewire hard drive, I receive several messages from the PowerCore Messenger.
This can occur when a FireWire hard drive is connected to the same FireWire bus as the Powercore. If the hard drive is inactive for a period of time -- for example, should you leave your computer unattended for for time -- the hard drive will spin down, and send a bus reset command, terminating all PowerCore plug-ins. Should this occur, you must save and exit your session and turn the PowerCore Off and then back On. Reload the session, and everything will return to a normal state.
Alternatively, you can put the hard drive on a different FireWire bus. There are several affordable PCMCIA / PCI / PCI Expresss FireWire adapter cards that will add a discrete FireWire bus to your system, preventing this from happening, even if the hard drive spins down and resets the system. Should you get an adapter card, we would recommend that you connect the hard drive to it's own FireWire bus, and combine the PowerCore with any FireWire audio interface device to the other FireWire bus.
Please note: A port is not the same thing as a bus. Many computers / FireWire adapter cards have multiple FireWire ports which are SHARING the same single FireWire bus. Please check with the manufacturer to see if this is the case.