Thanks everyone for the advice.
Just for the sake of leaving my troubleshooting path-
I ran disk warrior, I reinstalled FCP- both with no change.
It seems I saved the most obvious solution until last…
So far, it looks like the ‘bloated database’ is what happened. I never was able to ascertain exactly what caused the issue, but my work-around was to pull my sequences to a new project that did not include my original media bins. It seems to be rendering fine now. However, I don’t know what I did to bloat the database. Any thoughts on this point / things to avoid?
DB structure for reference: I had appx 30 hours of 4:3 NTSC DV25 footage all sub-clipped out with description/detials filled in and divided into various bins. I had a separate bin for audio clips (wav and SoundtrackPro), a separate bin for graphics (.png from AE, livetype,logo graphics), , a separate bin for clips prepped for FX (slow-mo, etc)
-TAJ