12.04/ RecordMyDesktop the sound isnt working...... Why?

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http://askubuntu.com – im unable to record sound using this app. the check box is checked for the sound, it just doesnt record sound. idk what to do. i have ubuntu 12.04 64bit. plus nvidia drivers dont work what so ever. so im just using the default ubuntu drivers. i looked up the site for this app. they dont give an instructions on sound for this program. any help me please??? the microphone sound input works with it. but it cant record system sounds. (HowTos)