I also experienced a crash to desktop after the tactical battle involving the same set of magical armor guarded by spiders.
LOG: Entered ruin;armor dialogue appeared; choose to fight; tactical battle started with spiders, left-clicked on the crown button to the left of the Interface, the pop-up tip for this button was "auto-resolve battle". I thought I would die so I clicked on the button to get it over with. Tactical battle ended and message popped up that said "tactical spells can only be cast in tactical area". Then the armor message popped up saying I had found the armor, then the main unit died message popped up, then it crashed to desktop.
I am posting all files requested to a text hosting site as indicated by the reporting sticky. Links to the text files are included below. Zip Dumps are in Dropbox as suggested, links below.
Debug Err: http://paste.org/pastebin/view/20842