When I try to change my transition time it stays on 0.1s, help!

Right, so when i add a transition to a still image i adjust the time to what i want, when i press done, it doesn't seem to change the time. Now I have tried turning the automatic transition off, changing the project properties. Almost EVERYTHING it's really annoying. But on some transitions it changes them and the time is coloured white, whereas the transitions I cannot change the times are a dark yellow. Does this mean it is a locked time? My still images range from 0.1s to 0.6s. Please Help! I'm using imovie 11.