Duplicate Install Entries on NIS12 Performance Events Graph

There are duplicate entries for some application installations on the NIS12 Performance Events Graph.  I ran Windows Update on 9/13/11 and installed eleven updates.  Those are listed correctly under the small disk icon.  On a later date I ran Windows Update again and installed one new update.  As expected, there’s a new disk icon on the graph, but nine of the previous updates are repeated along with the new update.  How can I fix this?