PowerPC :: Interface Hasnt Been Connecting To My Emac Properly?

I've been on a 1.25 GHz Emac for 2 or 3 years now. I use it for pretty much everything, but mostly messing about in logic 7. I have a M audio firewire 410 interface, and daisy chained into that is a Iomega firewire harddrive. Everything has been fine for a long time with the exception of some very occasional digital distortion.

But since sometime last week, my interface hasnt been connecting to my emac properly. When booting up, the interface's blue power light is meant to flash until it connects. But at the moment, it never stops flashing as it never connects.I initally thought the interface just needed its firmware updated, or had a dodgy cable. But I've also tried plugging my external straight into the emac, and that dosnt mount when its on its own either.

So far I've tried: 2 cold starts, hundreds of restarts/power cycles, zapping PRAM, reseting NVRAM, reinstalling the interface's firmware, installing the "combo update" and using the alternative firewire port. However none of this has worked.'ve spent a long time just trying to get it work and i really cant.Does anyone have any ideas of what I can do to get my firewire ports working ?