Your PPT file contains a too big WAV file, it seems this problem is caused by file size of your WAV file, I suggest you may by following steps to solve this problem,
1. Extract WAV file from your PPT file and save to a disk file,
2. Insert this WAV file into your PPT file by "Insert"->"Movies and Sounds"->"Sound from File" menus in MS PowerPoint application, (See "insert-sound.png" file)
3. Set some settings for this WAV sound, (See "sound-settings.png" file)
4. Save this PPT file,
5. Use "VeryDOC PowerPoint to Flash Converter" to convert this PPT file to Flash file again, then you can convert sound from PPT file to WAV file without any problem.