When changing link colour of More theme, Moodle stated "Some settings were not changed due to an error."

I changed the colour of links in the More theme, saved changes and Moodle reported back;
"Some settings were not changed due to an error."

Further down a section called "Could not save setting:" appeared with every other option in there apart from Text, Link and Background colour.

I didn't change anything else apart from Link Colour, so it shouldn't need to attempt to change any other settings in the first place?

EDIT: Recorded screen capture of issue :- http://screencast.com/t/2LHD8SS0pC