My source clips have SHRUNK!!!

I currently work with premiere pro cs3 and wasn't satisfied with the quality of the exported videos so I bought a mainconcept plugin and a few codecs and it worked just fine. The problem is that whan I opened one of my projects I noticed that the subclips in the timeline panel had black bands on them and the monitor showed absolutely nothing. To my surprise all of my source video clips had Shrunk, and though each one is actually over 1 hour in length they all have durations no longer than 1 minute. Please help me if u can, my work is on hold right now because of this and I don't know what to do. I tried deleting and importing the clips again, clearing the media cache files hoping a refresh would solve the problem and even a fresh install wasn't helpful as i guessed. I'm at the end of my rope here so any suggestion would be appreciated.