Okay, I did manage to fix my problem. I'm not sure what the cause of the problem was, ultimately. My fix was to simply re-upload the darkmatter template folder to my web site. Viola! Problem went away. However, since I don't know what caused this to begin with, there's always the possibility that this could crop up again. So if anyone has any suggestions for what I can check on (I do have a copy of the corrupt code in a back form so I could look it over) then I'd appreciate it.
("Pro" in this sense is being defined as "someone who has never been paid to do this stuff")
PixelPost version 1.7.1