In a posting entitled Quick Access Menu Questions started on Dec 9, 2011 it was reported that the Customise options of Minimise Ribbon and Show QAT Above/Below the Ribbon can appear disabled. I have had a similar problem and it appears to relate to an issue with docking controls.
If you take the example source posted in the zip file attached to Tina's reply on Dec 15 and add a reference to the Docking assembly then add the following to the xaml
between the end of the RadRibbonView and the Grid, run the app in a browser and the customise menu options on the QAT are disabled until the second RadDocumentPane is made visible.
I'm using Q3 2011 libraries, in IE9 on Windows 7.
Can anyone else reproduce this behaviour or suggest a workaround?