Welp, there we go. Clearly I don't 100% understand the custom file dialog I was attempting to use. Though I've never had it fail before, I'm sure you're not the last person who will run into issues with it. I'll stick with the shitty-looking default one if it means more compatibility. (I've PMed you for further testing in hopes of restoring the old dialog, though, please check when you get the chance.)
Edit: Updated to v0.9.0.1, I'll use the ugly file dialog until I have some idea of what the hell was breaking.