Norton Internet Security Plugin - Continues to prompt for update even though it has been updated.

About a week ago, a prompt came up telling me I needed to update to the latest version of Norton Internet Security Plugin. I ran the update and it installed version 1.5.0f4 of the plugin. But now the prompt to update to the latest version keeps popping up even though I have already installed it. Is 1.5.0f4 not really the latest version? What gives and how do I fix this?

 

Safari Version 6.0.4 (8536.29.13)

Mac OSX version 10.8.3

MacBook Pro, mid 2010