i'm finally convinced that i have this fixed, but it's bed time, now. i'm going to want to re-render pretty much everything for this project, but i actually think the mixing details will be pretty slight. even the stuff i was iffy on actually seems to sound pretty good.

my (hopefully) final analysis on this is as follows:

1) the initial problem was probably related to the codec install, although i can't state exactly what it did and will likely never know. it was a slightly different problem than showed up later on in the sense that it was at least consistent.
2) on the 21st, i ran the registry wipe. that would have broken the clock and put everything out of sync. i should have actually realized that, because i should have known to manually update the system drivers. i may have fixed the initial problem, but i wouldn't have been able to tell if i did because i broke the clock. since the 21st, this has been the primary problem, but i didn't realize it.
3) the reinstall ran the same registry wipe, which broke the clock again.
4) fixing the clock seems to have resolved the issue altogether.

i fully intend to get some serious work on this done tomorrow.