What is your source material and what are your computer specs?
To amplify on what PB asked...
These questions below may be for a different product... but the information you need to
supply is the same, for the products you use
More information needed for someone to help... please click these links and provide the
-Information FAQ http://forums.adobe.com/message/4200840
-Effective questions http://forums.adobe.com/thread/416679
-How to get help quickly http://forums.adobe.com/thread/419406
What are you editing, and does your project match your video?
Importing Video http://forums.adobe.com/thread/1065281
-and project settings http://forums.adobe.com/thread/1112086
When your project sequence is correct, you will not see a red line over your timeline
at first import, before you do anything to the video
Read Bill Hunt on a file type as WRAPPER http://forums.adobe.com/thread/440037
What is a CODEC... a Primer http://forums.adobe.com/thread/546811
What CODEC is INSIDE that file? http://forums.adobe.com/thread/440037
Report back with the codec details of your file, use the programs below... a screen
shot works well to SHOW people what you are doing
For PC http://mediainfo.sourceforge.net/en or http://www.headbands.com/gspot/
For Mac http://mediainspector.massanti.com/