I'm getting weird distortion and I don't know why!

[weasel walter]

Something is driving me up the wall. OK, I'm trying to master some stuff I'm working on and these irritating clouds of digital distortion are appearing ONLY when the rack tom is being played. Here are my specs:

-the original tracks were recorded straight to protools @ 44.1/16 or 24 (not sure yet -- I'm assuming they might have been dithered down to 44.1/16 which could be part of the problem) at a professional studio. I am confident about the engineer's technical skills.

-I mixed the 44.1/16 tracks in a fully upgraded copy of Sonar 1. I used some Blue compression plug-in on the rack tom and it definitely was not clipping in any way in the mix, nor were they eq'ed to be overly "phat". My final mix bounces were absolutely not clipping - they stayed peaking between -6 and -2 dB in general. My computer can definitely handle the mixdown - this is not a CPU issue. I'm absolutely sure of it - I've tried every possible combination of buffer speeds and submix bouncing and neither solves my problem.

-I'm mastering my final mixes in Tube Racks 24 version 2.0.1. I've been using this for years and I've been happy with it. I'm definitely not creating any overs - I'm using the brick wall limiting feature - but when I juice up my mixes, all of a sudden the distortion appears on the rack tom ONLY. It's not an overdrive-type distortion: it sounds like a fairly dense constellation of light digital clips.

If I listen closely to my bounced sonar mixes I can hear the distortion a little bit, but the mastering, of course really emphasizes it. For giggles, I tried recording my mix in real time through my soundcard directly into soundforge and I got the same bad result. The only times I can think of that I've had this problem was with another session I tracked at the same studio.

Please help!

ww