I downloaded your linked mp3 file and it looks fine. The encoding options are good and the file size isn't too high. I also tried streaming it directly in my web browser and again, no issues.
I took a look at your RSS feed and everything's working there, too.
I went to your website and began playing one of your episodes using the PowerPress player. I let it roll for about 5 minutes and it played just fine.
The best recommendation I can give you for listeners who report issues is to ask them to try a different way to listen. For example, if they're going to your website and pressing the play button and the playback is stalling, suggest that they download the file instead and listen to the file on their computer's default media player.
You mentioned one user reporting a problem with IE8 on Windows 7. Do you know of any other specific cases?