It sounds from your comment that you may have fallen victim to a pulldown enabled within the PT engine on one of the machines. I've seen this often-overlooked setting wreck havock on a session, and your sync drift mention leads me directly to this conclusion. Disable the pulldown (or pullup, whichever it is), and that should solve the problem hopefully.
If not, I'm very certain that the problem is at least focused on a pulldown/pullup issue, or a famerate mismatch is some sort. These are the two 'staples' which generate sync drifting issues. Hope that helps!
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"grossly out of sync"
what does that mean exactly? The first two things to check are:
1. was the 2pop at the head in sync?
2. was the 2pop at the tail in sync?
If you don't have a SMPTE leader with 2 pop on the head and tail of the QT the editor provided then you must, for this very reason. We use PT9 and there are no sync issues with layback or negs for film mixes being out of sync. But the process has to be rock solid, because there are many, many ways that mistakes can be made that put things out of sync, and I don't mean solely by the sound post dept. - there can be picture conform errors, undocumented picture edits, late VFX sync changes etc.... Are you sure the QT you worked to matches the final picture?