Problem solved. I was mistaken about the filenames. They indeed have spaces in front of them (this is not obvious when looking at them in Explorer and in the screenshot I provided). I removed the spaces, made the playlist in the usual manner, and then - BOOM! - Winamp now plays those files fine and dandy.
Thanks to DrO (and anyone else who might have tried to help) and sorry if I led you to a wild goose chase.
I guess the question now is: Why won't Winamp properly play audio files in playlists with spaces in front of their names? (If you've noticed the previous playlist made by foobar2000 I attached ( http://forums.winamp.com/showpost.ph...91&postcount=3
), it also has spaces, but foobar2000 can play the playlist, while Winamp still can't.)