Many people are reporting problems with Captivate 4 and Audio playback and recording. Adobe posted a fix on their blog and apparantly it does help some people.
I posted the solution below so if you have these problems try it out and see if it works for you.
We found that in some of Vista machines with Real tek or Sigma tel sound card audio inside captivate doesn’t play back. Some customers who use USB mic for recording narration also observed that device is not getting detected by Captivate. These issues were reported more on Vista and we have one solution to address both the problems. – replacing the audio dll’s , Steps
Close Captivate 4 if it is open.
Download the file kept at https://share.acrobat.com/adc/document.do?docid=a14e1bd9-dc10-4456-9cd2-44489809b78e
Go to your Captivate 4 install folder (ex: C:\Program Files\Adobe\Adobe Cativate 4)
Rename nsaudio.dll as nsaudio.dll.bak or anything which doesn’t have a dll extension
Copy the file from step 2 to Captivate 4 install folder
rename it as nsaudio.dll
Start Captivate 4
Try to play the audio /use USB – it should go fine
In case you can’t download the file from the above mentioned location I put up an alternative download link here (right-click to save file): http://www.cpguru.com/demonstrations/NSAudio_modified.adobe