UST Refuses to Render: "Invalid Filename" Error

[TheEternalChild7]

I'm attempting to make a UST for Alice Human Sacrifice, and I just finished the First Alice bit. Then I tried to render it as a .wav, but as soon as I clicked "Render WAV File," a little window popped up that said "Invalid filename," and it wouldn't let me go any further. I named my UST "Alice Human Sacrifice 1"; when I saw the error, I tried renaming it without spaces, and then without the 1, but nothing works.
Does anyone know what this error is about, and/or how to fix it?

 

[TheEternalChild7]

Well, I managed to get around the error by copying the whole UST and pasting it into a new file. I'd still like to know why it happened, though, so I can avoid it in the future. (If anyone knows...? ':3)

*Edit* Found the problem. When you first go to open the UST ( or in the Save As menu) in one of the boxes it should say "newfile.wav". The issue with mine happened because, for some reason, it just said "newfile". Adding a .wav to the end fixes the problem. (Just in case anyone else runs into this error. ':3)