I had a similar problem a day ago. The engine didn't like my SOUNDS* defenition. Gave me a black screen (no panels, buttons or texts showing). Still not sure why but changing the name solved my problem, but seems like you already done that. A bit unclear for me if you got problems with all TEXTs or just the "main" one.
Have you tried to comment // string = main_str;
and see if anything shows up then? (the text wont ofc, its just to test if it has to do with the string and not the *) or using a standard font like others have sugested?