There was a topic recently about a problem with MP3 files that were processed with iTunes and uploaded to MobileMe not playing in Safari on a Mac running OS X 10.6. These files would play OK in Google Chrome running on the same machine.
I've had problems with OGG files not working when uploaded to MobileMe. The same files played OK when uploaded to my account with Host Excellence.
When file names are being used in URLs its better not to have spaces and you certainly should avoid special characters. Separate the words in a title with hyphens if you need to.