After checking on a few other forums, another suggestion was to deactivate WooCommerce and then reactivate it. No guarantees, but it's worth a shot. (If you haven't deactivated the Canada Post plugin, that may also be an option...)
As for my own situation, I'm a little apprehensive because the issue seems to have fixed itself. Never a good thing since it cold appear again, but at least the store is working now.