Hmmm…weird. Most of the files within my current theme directory were listed as 666, but I was unable to edit them in WP. I changed them to 777, and now I can access them.
This brings up a couple questions:
1) Why did the access change in the first place? (Remember, I’d previously been able to make changes.)
2) Why can’t I edit files that are set to 666?
I get that (and full plan to make these changes once I get this problem fixed), but if my security settings are at the lowest possible setting, why in the world am I getting the non-writeable file error?