This box utilizes the t_standard class in the style settings; just removing the border value isn't an option as it'll effect a LOT of tables; you'd have to manually edit it out of the showflat.tpl and showthreaded.tpl files.
I'm hoping that in the future Rick seperates out some classes so they can be further tweaked (the online box, pagination boxes, wol, active topics, search results, etc)
