Sounds like your sequence settings inside of FCP are messed up.
Make a new sequence. Right click on the newly created sequence and choose "Settings..." from the drop down list. Once that dialog box opens look in the lower left corner of that dialog box and click on "Load Sequence Preset..." In there choose the appropriate settings for your camera. Then you'll have a sequence set appropriately. Now just copy your media form the old sequence into the newly created sequence. You may need to adjust the scale/distort of the newly pasted clips as they will have inherited whatever incorrect properties from the old sequence.
Ryan Holmes
http://www.ryanholmes.me
vimeo.com/ryanholmes
