I have a new HD TIVO with it's own remote control. This TIVO must replace the regular RCN cable box and you must use the TIVO remote with it. When I try to access the RCN On Demand channel, I am told to click Enter on the remote, but Enter on the TIVO remote prompts me to "Record This Program" instead of giving me access to the On Demand features. Is there anyway to get this remote to open up RCN's On Demand channels?

The remote has nothing to do with it. The TiVo HD can not receive PPV or On Demand; only a cable supplied STB can do that, at this time.