Created attachment 3684 Screenshot shows the "Dont Show This Again" added multiple times. 1. Clean install Xubuntu 11.04. 2. Turn off /on wireless Internet or do any activity that might cause the notification to appear multiple times. 3. Notice that the "Dont Show This Again" button is added to the notification bubble each time it reappears. (See attached screen-shot)
This does appear to a distribution specific issue. However I cannot verify this at the moment. see: http://ubuntuforums.org/showthread.php?p=10786766
Reading the forum discussion and the bug report on Launchpad, this can also be reproduced with notification-daemon. Thus, I would say it's a client issue and I'm closing the bug as invalid.