I recently ran into an issue with DoggCatcher not being able to download a podcast episode due to an error in the URL -- there was a leading space before the protocol descriptor: " http://path/to/file"
This is not a bug in DoggCatcher, but if the app were to trim any leading whitespace (like the Firefox XML viewer does) it would make it a bit more resilient. :)
Eric has a similar issue on his to do list 0001884: Auto-trim publication dates that have extra spaces in them - http://mantis.doggcatcher.com/view.php?id=1884 I imagine white spaces in the URL could be included.