For your information - there is a known issue in MindManager 9.0.240, 9.1.157 and 8.2.319, whereby intermittently ribbon and quick-link commands fail to function.
This appears in Windows XP, Vista and Windows 7.
The button will still be there and will appear to click when you hit it with your mouse, but nothing happens. This issue applies across the board to all add-in, i.e. this includes Mindjet extensions (like Remove Filters, Task Management and Export) as well as 3rd party add-ins (like TPAssist 2007). Mindjet acknowledge the issue but can't offer a solution at this stage.
In the meantime, if you click a button in the Ribbon and nothing happens, see if closing and re-opening MindManager resolves the issues. Alternatively you can find all our commands listed in the "Customize Quick Access Toolbar", so as a work-around you could add the missing command to the Quick Access toolbar.
(Updated 2/Mar/2011 - seeing issue now in Windows 7 and 9.1, plus Mindjet acknowledge they can re-create the issue for the "Remove Filters" button by simply having an add-on or Mindjet code display a dialog box or something before all Ribbon commands have finished building)
