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
For easy searching, download the product user guide PDF(s)
The individual CS5 pages also have links to the earlier user guide pages
CS5 User Guides - online and PDF (right click PDF link to save PDF to your hard drive)
Having black bars around the Video indicates that your Project Preset does not match the Frame Size of your Source Footage. What is the Frame Size of that Source Footage, and what Frame Size did you choose, at New Project?
The answer to your question is likely in those numbers.