Have you tried adding the missing route manually, from the RUT240 WebUI in Network -> Routing section, if it is routing problem only?
Otherwise, could you provide some topology picture of your network?
I would also like to look at the troubleshoot files from both, working and and current firmwares. To generate the files, access router's WebUI, go to System -> Administration -> Troubleshoot section and download troubleshoot file from there.