Hi Guys,
I've had this bug for quite some time. However, I just by mistake found a work around. I had the bug when the font size was at 40, with SFML 2.0 RC 16. However, when I set the font size to 20, the boxes around the letters disappeared. I'm not sure what the magic break size is for that. I'm just using the default font and compiling with the Visual Studio 2011 beta compiler. And the graphics chipset I've got is an old laptop ATI Mobility Radeon HD 4650, with 1gb dedicated ram. I only mention it because older posts attributed it to the graphics card. I've seen the same issue though on my Nvidia chipset in my other computer. I don't remember the chipset at the moment though.
This isn't all the code, but its the initializer code I'm using:
sf::Text mySfText;
sfText.setFont(sf::Font::getDefaultFont());
sfText.setCharacterSize(40); //note, 40 causes the bug, 20 doesn't seem to.
sfText.setColor(sf::Color::Green);
Hope that helps. -Brett