I'm not sure what triggered this problem with papyrus, but it was enough to crash my game. It may have started when Serana was with me when a dragon attacked in Falkreath (the town). See log file in attachment; no need to read all of the way through it, but I would appreciate some help getting a report for this into the tracker, because it isn't a typical papyrus error that I'm used to seeing.
DLC1SeranaLevelingScript -- Stack Dump.zip