A number of reasons (please correct me if I'm wrong):
1. Rumor has it that James knew what Cipres was doing and kept quiet because *winning!*. She says she didn't know, but who knows the truth about it.
2. This is not 100% clear, but I hope this is the gist of it. Radford and Duhamel talked about doing skating shows after retirement, and I believe the conversation was that Radford was retiring from skating all together. Then came the announcement of the J/R pairing and Radford never told Duhamel about it beforehand. He messed with her ability to earn money from skating because it's not like she can just up and skate with another retired partner like that.
3. J/R were terrible at Canadian Nationals, but they knew that no matter what happened, they were going to the Olympics anyway (because the Canadian Federation are morons). I believe James even bragged about it after the short program. And they finished 5th or 6th.