I tried moving a project folder onto my CPU harddrive to see if it made a difference if the files are coming from a USB source, and from the CPU harddrive the video files still don't playback.
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
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