[Acc 10.4.2.2, W 8.1u, HP Pavilion g6-2306el]
Here are the steps to try and reproduce the bug:
1. Run one or two other Windows programs.
2. Run Accordance.
3. Open at least two tabs with whichever Bible text.
4. Open another tab (again, with whichever Bible text)
5. In this new tab, use the Contents command (Ctrl-Shift-C)
6. When the 'select window contents' dialog appears, use the Windows key combination to show the Desktop (WinKey-D)
7. Try going back to the Accordance program window using the Alt-Tab, or even by clicking on its icon in the Taskbar.
I couldn't go back to the program. The workaround would be to press enter after selecting the program even though the program window can't be seen: this would select the first option in the 'select window contents' dialog, which seems to prevent the program window from appearing correctly. The next time you select the program (by Alt-Tab or clicking) the window appears normally, with the new tab having the contents of the first option in the 'select window contents' dialog.