tom omalley 0 Newbie Poster

Hi, I have both Adobe Pro and Adobe 6.5 loaded on a Gateway model mX widescreen. I removed Pro when all of my footage dubbed to the computer went into folders in 6.5.
Question : I have accidently done something while editing that turned all of my transitions into red "X's" and I've had to manually go through the entire 1.5 hour video and insert new transitions.What did I do and how can I correct this to take the default cross fade trasitions iso I don't have to go through and do all that work on all my video's?