This is got me confused as ever. I have a 4K R3D RED clip that I drag into my 1080p timeline. Premiere says the scale is 100%, which can't be right because the whole image has been reduced to fit in the frame. If I set scale to 99% or 101%, it displays at the correct size (larger than the frame).
Any ideas about this one??
Running CS5.5 on Mac here.
Check Preferences > General and see if you have the "Default scale to frame size" preference set. If not, right-click the clip in the sequence and see if "Scale to Frame Size" is checked there.