I don't have a RPC plugin installed into my system. But I know that there are issues with RPC. Someone told me RPC also has a plugin named colorcorrect.dlm. if that's the case make sure that both are available to max (you may need to rename one). Also since for MAx 5.1 you need to use ColorCorrect compiled for max 4.x, please make sure that you upgrade your max 5.1 to the latest point release (I think the latest patch is SP1). Besides that I'm not sure what's the problem. I'll check it by DL'ing RPC demo when I have time.