I've been using the IE Net Renderer website as I don't have IE6 installed.
Having just tried your non-Pro gallery, I get the same results (fallback text with IE6 rather than just blank screen with IE7 and IE8).
However, you claim that the non-Pro gallery actually works in IE6 so I guess the results from IE Net Renderer are inconclusive.
If the non-Pro gallery did work, then swapping out the swf for the Pro version shouldn't have made a difference.
With regard to your other questions:
Can I define the displayed Browser title and the complete background color with the pro version?
The browser title goes between the <title></title> tags in the <head> section of the HTML page.
The background color can be set using the Flash parameter bgcolor... something along the lines of:
swfobject.embedSWF("simpleviewer.swf", "flashContent", "100%", "100%", "9.0.124", false, flashvars, params);
SimpleViewer Support Team