When a section of a file, which is part of a running torrent, cannot be read I get a SIGBUS error. When session storage is active and rtorrent tries to rehash files on next start of the program this makes rtorrent automatically crash again once the hash check tries to read the same section of the file.
Is this happening again? Full report: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=698554