Welcome to the forum.
Unfortunately, we'll need a lot more detail about your Project, the Assets used and your system to tell. The more details, the better. Without these, it will only be guessing on our part.
Good luck, and looking forward to the details,
This is aimed at Premiere Pro, but may help
A link with many ideas about setup http://forums.adobe.com/thread/436215?tstart=0
Many ideas are generic enough they have helped some Non-Premiere users fix problems
Also, work through all of the steps listed at http://ppro.wikia.com/wiki/Troubleshooting
If your problem isn't fixed after you follow all of the steps, report back with the DETAILS asked for in the questions at the end of the troubleshooting link
Thanks! I'll try your suggestions and will report back with more details.