Update to the above post: Finally got off (on?) my lazy ass and did some more testing. Trajectories is NOT the sole cause of my crashes. It's somehow due to the combination of Trajectories (v1.6.5a) and Reentry Particle Effect (v1.2a). With both installed and no other mods except Module Manager and KER (had to leave it in since I had the KER chip's on my craft) the crash is 100% repeatable like before. Removing either mod stops the crashing. This is actually nice, because I'd rather play without Reentry Effects than without Trajectories.
Screenshot of the failure:
https://www.dropbox.com/s/vtvknesziu73ulm/Screenshot.jpg?dl=0
(The image won't embed for whatever reason.)
The lower trajectory in the upper-right of the image is actually below 70km, and shows up red until the game freezes.
Files from the crash report folder, in case anyone's interested:
https://www.dropbox.com/s/ielh0ybl7oalxeu/crash.dmp?dl=0
https://www.dropbox.com/s/vzc9p7ciizf5woz/error.log?dl=0