Hi Lucian.
I finally got around to trying the suggested fixes and they worked perfectly. I ended up deleting 4 WP Activity Log records from the wp_options table and resetting the plugin’s settings, and now everything is working as expected.
Thanks!
Note that Brunelleschi 1.5.8, the latest as of this writing, includes a newer Respond.js and does in fact fix the IE 8 crash bug.