Can't add more theme components

[grassfrog]

What doesn't work pressing s button or actually saving?
Could just be a js error

When you press the button, the add field wasn't displayed and the url had a # at the end.

At any rate, I resolved it by re-FTPing the admin directory but there is still no logical reason why the error occurred or any clear instructions on how to avoid this in the future (other than ONLY FTPing fresh instances, which isn't always an option).

I still get similar errors if I build a new GS site in a subdirectory then move it (using SSH) to the main one, even though ownership and permissions are correct. I'm baffled.