I just got this error message when trying to edit content (existing block) on starting page of my site. Editing other pages work fine. Discovered this today, haven't updated it in the last few weeks. I'm wondering if today's PHP update by my ISP could be the culprit. They did this update because the C5 nightly updater apprently failed with the old PHP version.
Any ideas are much appreciated, thanks!
PS Please don't ask me to update to newer version of C5. My custom templates don't work with newer versions, so that's not a solution at the moment.
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