firewire woes

[firebucketpatrol]

i'm running: protools le 7.1 on a powermac g5 (tiger 10.4.11, dual 2.7 processors, 2gb ramm) via digi002r +micronet 150gb firewire drive (roughly 100gb free). i have two internal hard drives (both are maxtor 250gb), one for system (pro tools is installed here) and one for music/session backps.

i have been using this setup for 2 years without incident. within the last couple weeks, with rapidly increasing occurrence, i have been getting error messages (-9073, -6086, & -6093 i believe, the typical "increase playback buffer" and one i hadn't seen before saying "can't get audio from drives fast enough"). it's not the first time i've had the old "increase playback" message, usually i just shut down the 002, swap the fw ports and the problem is solved.

i have tried:
- cleaning up the session (deleting unused, consolidating most regions)
- erasing the contents of my drive and reloading only the few sessions i need to work on this week
- restarting/reloading/switching ports and everything else i can think of akin to blowing in an old nintendo game
- changing cpu/playback allowance
- using less plugins
- running a backup session on my second internal drive (which worked fine)
- profanity

before i cleaned it out, my fw drive was getting pretty full, and had been used without any maintenance since i first fired it up. is it possible that it needs to be de-fragmented? if so, how do you go about doing that on a mac?

cheers!
-nash

ps. i'm in the market for a new FWHD regardless, i've looked at lacie and g-tech, i'd like a terabyte, any recommendations?