I received an email last night from Google AdSense saying;
We wanted to let you know that Google Pack Referral conversions were not recorded for a 24 hour window beginning early July 5th and ending mid-day July 6, Pacific Time. Conversions from this period won't appear correctly in your reports and you won't have received the related earnings.
Please know we're working hard to reimburse you for the lost revenue in the coming weeks. We sincerely apologize for any inconvenience this might have caused.
The Google AdSense Team
Wow, "Please know we're working hard to reimburse you for the lost revenue in the coming weeks." I guess these things happen to even Google.
Forum discussion at WebmasterWorld.