Color markup in message settings child blocks until parent window is closed

I use ubuntu 12.04 x64.
I installed ubuntu in Dutch, but I try to translate the menu items to make it possible for anyone to reproduce this bug

When I go to "Settings" >> "General settings" >> tab "View" >> subtab "Message", and click "Edit" next to "Enable color markup in message" than I can't edit anything or close the child window that appears, until I close the parent "general settings" window. This shouldn't be the case. The parent window should lock and the child should be active.