Thanks for the comments, mettelus.
 
I think now that my problem was definitely using 32-bit Melodyne with 64-bit X3. I managed to work with it for several hours this morning and had no trouble whatsoever.
 
Thanks for clearing up where exactly the buffer settings are, though. I'm not crazy about having to reset them depending on what I'm doing, so I'm just going to leave them the way they are for now.
 
I also posted the above screenshot and question on the Celemony forum and someone there said I'd set the buffer in the right place. Of course, I don't know if that person knows Sonar or if he was just assuming something.
 

Oh, and about posting images from Google Drive...
 
Turns out, you can't just plunk the URL Google gives you straight into the message. You have to massage it first. The following post summarizes the procedure about 3/4 of the way down the page: http://www.blowoutcards.c...-drive-forum-post.html