It is possible that you can orient every pair of photos in the project successfully but all together they will not. The reason has to do with scaling. A scaling step is carried out when orienting three or more photographs that is not carried out when only two are oriented. So this failure is usually a failure to scale correctly. Scaling will fail because of one or more bad referenced points, because one of the camera stations has an incorrectly defined set of camera parameters or because there are insufficient points shared among a minimum set of photographs to affect a scale. This last problem is corrected by marking and referencing a few more points across as many photographs as possible. The other problems are resolved by studying Audit, Point Audit and the Camera Viewer Dialog.
You should also make sure that all the photographs have the correct camera assigned (i.e. the camera parameters, including zoom/focal length, match the photographs).