On Friday morning we were the first to report widespread panic around Google AdWords quality score drops. It turned out, as expected, to be a Google bug.
Google said then "we're currently rolling out fixes and expect all accounts to see normal reporting by tomorrow." The fix rolled out as promised on Saturday, where they posted on the Google+ social profile that it has been fixed.
There is a caveat. If you paused any campaigns because of the bug, when you unpause it, it can take an hour or two to show the updated quality score.
Google wrote:
The bug affecting quality scores that we posted about yesterday is now fixed. Thank you for your patience as we worked through this. If you paused any keywords yesterday, we recommend that you un-pause them now in order to see the correct scores. These paused keywords will not reflect the correct score until one or two hours after being un-paused.
Please confirm your quality score is back to normal.
Forum discussion at Google+.