i have not encountered the problem with the chat rooms since i do not use that feature. however, updating might be what you need. if you use ubuntu, RHEL/Centos , Fedora core or any of their derivatives, you can get information on how to install an updated version from http://www.pidgin.im/download/ubuntu/ . alternatively, you can download the source code here http://www.pidgin.im/download/source/ and compile it yourself. i however advice you to try installing the .deb or .rpm file and not go down the compilation road as things could get ugly if not done correctly.
again, i hope this was useful.