groundyonly

Hi all, Please can you help me! I am using 3.04. Recently when I have cut buts out of videos to get the clips I need, the program is leaving the rest of the original clip time-- e.g., if I take 10 seconds out of a 2:10 video, then 2 minutes-- as blank screen, and when I export, it's black screen. What's happening and how do I change it? I have looked in the editing and effects areas and I can't see anything that will let me change that! Never used to happen... I must have done something I didn't mean to at some point, now it happens all the time. Cheers