So, after porting my characters, input data, and everything else in the profileCollections folder over from  v0.9.2a to the 3.4.8 single player demo, I get the following error message in both the development console and player log: 

IndexOutOfRangeException: Index was outside the bounds of the array.

  at QuestTrackElement.Handle_QuestTrackInfo () [0x0019e] in C:\Users\Nate\Documents\_Atlyss04\Assets\_SCRIPT\_GUIScripts\QuestTrackElement.cs:43 

  at QuestTrackElement.Update () [0x0002a] in C:\Users\Nate\Documents\_Atlyss04\Assets\_SCRIPT\_GUIScripts\QuestTrackElement.cs:15 

Fortunately, subsequent launches of the game are free of such errors (my best guess is the cause is a mismatch between the listed User name and the actual one)

Abandon all your quests.

That did the trick, thank you!