On December 17, we announced Google's plans to push out a data refresh for the Sandbox due to some issues and bugs that users have been encountering.
The initial Sandbox refresh was scheduled for December 19th. Apparently, though, Google has announced that the Sandbox update has been postponed for about 2 weeks. No further information is available.
Update 12/30: According to the Google Groups thread, the update occurred on 12/29.
Forum discussion continues at Google Groups.