Hey Andy,
Tried installing Chrome and that is not opening the audio samples either.
What is strange is Firefox version 20 opened the top half of the samples, but not the bottom half. When I upgraded to version 21 they all stopped playing. So, I did have audio at one point for some of the samples.
Not sure what to try now.
FYI: Pro Tools is on this machine and using Avid CoreAudio manager.