Ben, because this board is always named */bbs5, all the posts have titles like */bbs5/0056.html, which means that your browser has seen these file names before.
Clear out your temporary internet files and your internet history files [for MSIE, or the equivelant for Netscape] and you'll be golden.
Yes, it's more work than you need to do for other sites, but (a) it's gonna get better someday when the powers that be upgrade the message area, and (b) it's a small price to pay for participation in the grooviest piece of real estate on the net.