Maybe it's the PNG type that isn't right, I suspect Visionaire to be unable to operate with PNG-8 (Indexed-color), I've tried the PNG-8 format with the font image and nothing was shown, then I re-exported the file in PNG-24 (TrueColors) and it worked.
Do you use photoshop ? If you do, don't use 'Save as' to save to PNG, use the 'Export for the web'
I also had the 'black screen' issue, then I installed Vis 4.01 and no more issue (resolution 2560x1440). But I still have several crashs for some reasons