Just tried to open the blueprints after playing awhile on the last crash/save I posted, and everything was going fine, but crashed as soon as I pressed 'b'

Just had some biters eat a few things at the top of the main base, ran up and hosed 'em down with a flamethrower ..

.. and then just crashed out with an "unexpected error."

Attached is the save (bug attack happens a few minutes after starting) and the log file.

EDIT: Running vanilla, no mods ...