What OS are you using and what kind of clip is it. Premiere does not take kindly to all kinds of formats.
Analyze the clip and post a screendump of the clip in treeview.
Did you do the below to be sure your video is properly "seen" by PPro?
What are you editing, and does your sequence match your video?
For CS5 and later, the easy way to insure that your video and your project match
See 2nd post for picture of NEW ITEM process http://forums.adobe.com/message/3776153
-and a FAQ on sequence setting http://forums.adobe.com/message/3804341
thanks for your help guys it seems to be okay now aslong as i use mp4 format and not avi