First of all, I have read the following:
When I press F12 or select "Developer Tools" from the Tools menu, nothing happens.
The problem is not that the window is open, but offscreen (it doesn't show up in the taskbar or alt-tab). Also, there is no "IEDevTools" registry key anywhere in the registry (I did a search).
This is on a freshly-installed Windows XP VM used for compatibility testing.
Is there any other reason, besides window position and rogue registry settings, why the developer tools would not display?
Immediately after IE8 loses focus to the tools window (right after pressing F12):