It sounds like it might just be a visual glitch. Try moving the window after you've opened it, or minimising and then restoring it, or dragging the mouse over where the text should be (as if to select it). Do any of these actions restore it to visibility?

Sometimes when I open a class's source code I can't see anything besides for the first 'I' of the first import (And the red caret). I restore all the text by pressing Ctrl+A.

Dragging the window around the screen helped a bit, although it became a stretched version of the source code. It's progress but still won't do. Dragging the mouse over the window itself and selecting something didn't work either. Decided to try something out and change the font of the text through the preference window even though I'd just put in the same font size. This fixes the problem temporarily by just making that one particular file show up, all else disappear as usual except if I do that font trick again. Got any other ideas?

Tried doing ctrl+A, sadly that didn't work :( Although, I did do that font trick I lightly described up there in my latest comment. It's better than restarting the entire program but still, a solution to actually fix this visual glitch would be awesome.

I also have the problem a lot of times. I don't really know what exactly causes it (or when exactly it happens), but either the entire window is blank or for example when an error occurs, the position of the error is visible (like one letter) but the rest is blank. If it is a compile error, it also sometimes opens the class code itself, when clicking on compile (in the class), it jumps to the correct line. Resizing a blank window only results in changing color between all black and all white. The GUI gets visible when hovering with the mouse, the code itself has to be selected (mouse pressed and dragged around). This has to be done for each individually blank tab. Ctrl+A makes everything visible, the disadvantage is that it moves to the last line and doesn't stay where I was before.