This sometimes happens to me. Try deleting your temporary files - you've probably partially downloaded an episode and each time you try to play it the browser opens the part-downloaded file.
Tools > Internet Options > Delete (Under Browsing History) > Delete Files

Good luck!

Same problem here.... Even with my own episodes, even with other users episodes....

And everyone who I sent my PodOmatic had the same problem...

And I can see this problem when I hear an episode, or when I try to download it (in same cases, I tried direct to download the episode, and there was the same problem.... Download about 10% and stop)...

I hope they fix this problem, very soom....