I've recently bought Recordpad 4.01 for Mac OSX. It opens and records with no problem, and the recordings show up in the 'Find and play recordings' window, plus the file size shows they have content. I can click on them in the recordings list and they play back, no problem, and with very good quality (I use a Shure mic and M-Audio Fast Track).
However, when I then slick the 'Save' icon and save the file to my designated folder -- either as .wav. or .mp3 -- the file is listed in that folder but has a Zero Kb files size, no content and can't be opened, either by Recordpad, or WavePad.