Don't be surprised if UA calls you and asks that you cancel one of your overlapping segments:
http://www.flyertalk.com/forum/unite...ervations.html
Because chronologically, it looks like you have:
11/19: DEN-SFO-RNO (res1)
11/19-11/24: RNO-SFO-SEA-NRT-way more-NRT-SFO (res2)
11/24: SFO-RNO (res2; you want to skip/cancel)
11/24: SFO-DEN (res3; you want to take)
11/25: RNO-DEN (res1; you want to skip/cancel)