We've got an issue where we cannot save changes to CMS pages via the backend. However, changes to product pages save completely correctly via the backend. I have tried rolling back the SUPEE-7405 changes, but we still can't save content changes. The rest of the store seems to be functioning fine - we can still take orders and so forth.
Chrome shows an error 500 when you try to save. I don't see anything in the logs, but I'm not sure I'm looking in the right place.