I'm still running OpenBSD 4.1-generic and rtorrent 0.7.1 on a home server for months now, and I never really had any problems, except having to raise the limit on maxopen files. You could try checking yours with ulimit -n. If the problem is not that, then I'm clueless =(
-- An OpenBSD user... and that's all you need to know =) Please, send private emails to [EMAIL PROTECTED]