At first, no one could figure out what the issue was. Later, on 6/20, the PSN people updated the message boards to let gamers know they were examining the problem in an attempt to fix the issue. 

Morgan Haro, SCEA PSN Community Management Team Member, had this to say on the message boards:

This morning at 8 a.m., an update was posted on the community boards:

The post went on to say that if there were any further updates, they would be posted between now and then. Gamers can now only wait (possibly banging our heads against a wall) for the fix to come. 

For more information, visit the update thread at Playstation.com.