If you're having trouble finding a hidden dialog box that's preventing you from accessing an application, try downloading another great utility from Nirsoft: WinLister - available for download here. WinLister will show a list of applications that are currently running on your PC.

One column lists the topmost applications. Under Options you will be able to direct WinLister to display all hidden windows. Right-clicking on any one application will give you the option to bring the application to the top.