Excel 2007 Quick Access Toolbar Problem witn VBA Macros

Hi there.
I have 3 different files, each one of them has macros and I use buttons in the Quick Access Tool Bar to run the macros.
When I have more than two of these files open and I run any of the macro that opens or closes one of the other files, the buttons in the QAT are duplicated. How can I avoid this behavior, is there any way to lock the QAT so it doesn’t get modified? It is important to mention that I have no problem with the macros... they run OK without any errors, but I don’t understand why the appearance of the QAT changes.
One more thing. When I run the macro step by step with the Debugger nothing changes in the QAT and everything goes fine.
I appreciate any information about this subject.