This is message is posted on the theme editor page.:
You need to make this file writable before you can save your changes. See the Codex for more information.
I tried to resolve the issue by adjusting the numeric value under file attribute in Filezilla, from 755 to 666 as was recommended here: http://wordpress.org/support/topic/50863?replies=15 , but the numeric value resets itself to 766, but then I get a blank page when I try to open the control panel.
Everything was fine until Sunday evening. Anyone else having this problem?
Some help with this would be appreciated.