Your image didn;t show so can;t say for sure but UI problems like this are usually fixed by deleting the Aperture preference file. Do the following
Close Aperture. Triple click anywhere in the line below to select it:~/Library/Preferences
Once selected right click or command click and select Services in the contextual menu then select Open
You will be in your Home Library Preferences folder.
Once there look for the file com.apple.Aperture.plist move it to the trash and restart Aperture
If you still have problems post back