No fix with such scanty information
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
If you have a red line over the timeline after importing a video and before adding any effects... your project is wrong for your video... read above about codecs
Once you know exactly what it is you are editing, report back with that information... and your project setting, and if there is a red line above the video in the timeline, which indicates a mismatch between video and project
More information needed for someone to help... click these links and provided the requested information
Welcome to the forum.
To be of any help, we need a lot more information. John T., has linked to many good and useful articles, that will help you to help us.
The two major causes for what you describe are:
Good luck, and please let us know a lot more.