[Joe Mendelson]

hi richard -

no great ideas, but i can tell you what i would do next (which by now i'm sure you've tried. but i don't feel like working, i'd rather DUC!).

1. you've narrowed it down to an automation problem. did you check plugin automation? pan, etc? i agree it sounds like some super-dense automation breakpoints or something bogging the system down. so check all the different kinds of automation.

2. copy a chunk (all tracks) that goes across new audio to empty space to new audio, and paste it way down the timeline, after your other stuff. then try playing across the change-over there. same issue?

3. and last but not least, the old import all the tracks into a new empty session. as you know, sometimes this seems to clear up these funky problems. the old session is somehow corrupted, and the new one works. which reminds me - a subset of this method is that sometimes its just one track that is corrupted. have you done any selectibve track de-activation (with the automation on) to see if its tied to a specific track(s)?

best i got, and i'm sure nothing you didn't think of. let me know if you figure out the root cause, or the work around.

stay cool -

joe