Is there some reason you have not updated PPro 5.0 to the latest version?
All Adobe updates start here and select product, read to see if you need to install updates in number order, or if the updates are cumulative for the individual product http://www.adobe.com/downloads/updates/
More hardware information might let someone answer your question... such as brand/model microphone
-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