I have a few podcasts that sometimes have files in its list that have spaces in the filename, and PodNova tries to download the files, but then fails with an error message, just like this one:
Can't grab http://www.webwereld.nl/attachments/free/WWpodcast 08dec06.mp3: The requested URL was not found: http://www.webwereld.nl/attachments/free/WWpodcast 08dec06.mp3