I have an application that includes two basic dialogs (an "about" and "registration code input").
Both dialogs are build from resource:

Code:
RESOURCE DIALOG r_about_dialog
	{
	flags= EEikDialogFlagNoDrag | EEikDialogFlagCbaButtons | EEikDialogFlagWait | EEikDialogFlagButtonsBelow;
	buttons = R_AVKON_SOFTKEYS_BACK;
	items =
		{
		DLG_LINE
			{
			type = EAknCtPopupHeadingPane;
			id = EAknMessageQueryHeaderId;
			control = AVKON_HEADING
				{
                headinglayout = R_AVKON_LIST_HEADING_PANE_POPUPS;
				};
			},
		DLG_LINE
			{
			type = EAknCtMessageQuery;
			id = EAknMessageQueryContentId;
			control = AVKON_MESSAGE_QUERY
				{
				message = "";
				};
			}
		};
	}
RESOURCE DIALOG r_activation_dlg
    {
    flags = EAknGeneralQueryFlags;
    buttons = R_AVKON_SOFTKEYS_OK_CANCEL;
    items =
        {
        DLG_LINE
            {
            type = EAknCtQuery;
            id = EGeneralQuery;
            control = AVKON_DATA_QUERY
                {
                layout = EDataLayout;
                label = STRING_activation_pwd;
                control = EDWIN
                    {
                    width = 21;
                    lines = 1;
                    maxlength = 20;
                    };
                };
            }
        };
    }
And they both work OK, except that the "buttons" are not displayed for any of them. Instead, the CBA becomes semitransparent and shows the buttons of the application underneath the dialog.
The dialogs respond to softkeys OK. It is only that buttons' tags are not displayed.

The application is displayed in whole screen (SetExtentToWholeScreen()) but, as far as I know this is not a problem. I have done quite a few apps that work on whole screen and display the dlgs OK.