Tested on Ubuntu 11.10

When alt-tabbing to a window with a newly opened dialog window, the window (or at least the buttons) does not have keyboard focus.  This is best demonstrated with an example:

1. Open the same file (any text file) in both GVim and gedit
2. Modify and save the file contents in gedit
3. Alt-tab to GVim (a "W11:Warning" dialog window will appear)
4. Try to close the dialog box by pressing the Return key

What happens:
Nothing.

What should happen:
The "OK" button on the dialog window should have keyboard focus, and pressing the Return key should close the dialog window.