This wouldn't happen to be slightly rectangular, and at the start and bottom of where the text would be would it? Because if so, that happens every time you try and start to type the text in CS. It's a way of showing you where your text starts. I had a look through CS and couldn't get any other sort of black box to appear, so as far as I can tell, it would either be a program glitch (in which case I would re-install, that doesn't take too long anyway), or you cannot see the text because the text colour is White against white background, black against black background, etc.