For what it is worth and, further to my previous post. :)

I just completed another mission with an assassin and made a point of accepting the mission as complete whilst her temporal shield was activate; the game crashed as before. It would seem to be a combination of an active shield when clicking on that accept button.

I do believe so, as I have only had 3 game crashes as of this time. The first was whilst playing an assassin who had the temporal field running when I accepted the mission, that was a few days ago. The other 2 crashes were today, again when I accepted the end of the mission and, both occasions I had the personal void shield up on a crusader.