In the Delphi 2009 RAD Studio, there is a drop-down combo box where you can select the desktop configuration, i.e. "Default Layout", "Debug Layout, "Classic Undocked", etc. This has stopped working for me, i.e. when I select a desktop, nothing happens. I think I once "customized" the toolbar, by removing the drop-down combo box, and then I added it again, and ever since it has been dead. Is this a known bug? Is there a cure?
Is it still switching configurations when you run the project or when you go back to coding?
Have you tried to create new custom configurations, save them and switch manually with the combo?
My guess is it's something wrong saved in the Registry. You could try (after saving your current registry) to get a (good) D2009 registry from another install where it works, and apply it to your machine. If it works again you'll have a way to figure it out by diffing the regs. If not you may have to reinstall D2009 (or at least try"repair").
DISCLAIMER: yadda yadda about touching the Registry...
Create a new user account on your computer, call it "Testing" and log in there. Now load up delphi and try this desktop layout button. If it's now working in this alternative desktop account, then it's something in your registry settings under this key:
HKEY_CURRENT_USER\Software\CodeGear\BDS\6.0
Try setting the keys named DesktopName and RuntimeDesktopName under the Session key
HKEY_CURRENT_USER\Software\CodeGear\BDS\6.0\Session\DesktopName=Default Layout
HKEY_CURRENT_USER\Software\CodeGear\BDS\6.0\Session\RuntimeDesktopName=Debug Layout