Clear all button on voicemail is delayed (iOS 5)

After I delete messages on visual voicemail and then go to "Deleted Messages", the "Clear All" button remains greyed out for 5-6 seconds and then becomes available. It never used to do this - it would be available as soon as you opened up that screen. I've rebooted my phone, but that has not helped. I usually am only clearing 1-2 messages, not a whole bunch. Any ideas?