The Google Analytics Team announced that an issue within their system is causing a problem with reports for April 2011. This problem results in 0 visitors showing on reports generated using custom reports, advanced segments, or secondary dimensions.
The Google team is hard at work on the issue and has discovered the source of the problem. They have assured everyone that no data was lost; it is only a problem with reporting the data. The data in question can still be viewed through standard reports.
They have begun restoring some of the information and foresee having complete data available for Analytics Reports by May 23. A partial restoration has been made and they will continue to work to restore the information for each day that was impacted.
To view the announcement, you can visit the Google Analytics Blog. They will post updates on their blog as the issue is resolved. As always, the team here at Propertyware will monitor this situation and any situation that impacts our clients.