I have the same problem.Moterboard with AMD processor and 100% utilisation. Few days ago did upgrade from 2.9 rc7 to rc9. Before all works ok, now after few hours always have 100% processor load. Working only telnet-ssh connection. The only way to resolve this problem is reboot router. Its AMD processor question?
I did remote upgrade to rc10 3 hours ago. Had some affraid (router is about 6 km away from me on roof 10floor bulding) but working fine. Processor have normal load (up to 60%).