hmmm
well, i found the problem (sort of) the noise is only reaching the stereo buss thru one of my hardware inserts, a demeter spring reverb. it only happens after i have renderered a few fades and only squeaks when my session is playing thru a fade. i am stumped. muting the spring's aux track makes the noise stop. very odd. i will post an audio file of the noise at:
http://www.toddburke.com/duck
btw - these sessions are running at 88.2/24 and again, this happens regardless of clock source.