PunBB logs me out when I request a lot of pages at once

I was screwing around with bookmarklets and decided to try "open all links," which is as follows:

javascript:(function(){var n_to_open,dl,dll,i; function linkIsSafe(u) { if (u.substr(0,7)=='mailto:') return false; if (u.substr(0,11)=='javascript:') return false; return true; } n_to_open = 0; dl = document.links; dll = dl.length; for(i = 0; i < dll; ++i) { if (linkIsSafe(dl[i].href)) ++n_to_open; } if (!n_to_open) alert ('no links'); else { if (confirm('Open ' + n_to_open + ' links in new windows?')) for (i = 0; i < dll; ++i) if (linkIsSafe(dl[i].href)) window.open(dl[i].href); } })();

on the PunBB forum index, http://punbb.org/forums/ (85 links).

The first few pages load fine, but then I suddenly get logged out, and remain that way for all pages loaded thereafter; very noticeable because the color scheme goes back to the default (I've changed it).

Now, I know most users will not try to load 85 pages at once, but does this indicate some sort of deeper bug or unreliableness? I'd be interested in any thoughts on what might cause me to get logged out when doing that.

I tried "open all selected links" with 11 links selected and there was no problem.