Earlier in the day, Reuters reported that "Google is blocked in China" — And, Google's Mainland China service availablility chart also said that Google is blocked in Mainland China. But tweets from Beijing and Shanghai say "they've full access to Google through regular DSL connections.
Google via email responded "Because of the way we measure accessibility in China, it's possible that our machines could overestimate the level of blockage. That seems to be what happened last night when there was a relatively small blockage. It appears now that users in China are accessing our properties normally. Please also note that the dashboard isn't a real time tool."
The fact that the dashboard doesn't update in realtime is probably what lead to today's reports as to whether or not the service was working. When asked what specific issue caused the blockage, Google responded that they had nothing more to add.