i've just bought a profire 2626 and i experienced clicks during recording, so i started trying different connections and workaround for that problem.
i've the first mac pro 2.66ghz (bought in september 06) with 3 uad card, no slot free to add a firewire card, an rme fireface 800.
first i've disconnected everything from the computer except the profire and the clicks remains.
than i've noticed the profire was connected to the front firewire 400, i've disconnected it and connected to the back firewire 400 port, than i've tried and no clicks happen, so i connected the rme fireface 800 to the m-audio secondary firewire port.. than i've engaged all the 8 channel in the m-audio the 8 channel in the rme connected via adat.. and i've recorded 16 tracks together (no audio.. just the noisefloor to see if some clicks happen.. they happened also without nothing plugged on the input.. just record engaged.. and now they dont)
i've done that to use all the bandwidth i can and i've recorded 200 bar more or less, no clicks
so i'm happy and i like to share that
p.s. if in the future i report other clicks problems i'll write them here.