Mac or Windows?
You might trying putting a "Pause/Resume Script" script step just before you display the dialog, specifying a pause time of, say, .01 seconds (1/100th of a second). You won't see any pause (because the pause is for only a tiny fraction of a second), but this may cause the screen behind the dialog to refresh so as to be visible when the dialog box appears.
Thanks for the suggestion. I added a .01 second pause and the dialog box did display over the layout after a brief flash. The only problem is that there are dozens of scripts with hundreds of dialog boxes that will need the be updated
BTW, I'm using the windows version.