Can't update theme - trying to save gives error

I'm trying to make a few minor changes, for example, the text on the home page. When I try to save I get an error message: "There has been an error saving your changes."

Thanks for helping resolve this matter.

ALSO, when I gave your support staff access to my site, and tried to leave info about the problem in the provided field, clicking the "save" button didn't do anything.