Try going into the video settings and setting the render quality to the highest setting. (that's what worked for me). I didn't play around to figure out exactly how to make the problem start and stop, I just stopped changing things when it worked.

I might have found a workaround. Or maybe only a temporary fix...

If I change the render quality to "highest", the missing text reappears.

Same thing is happening to me as well. I haven't played since July, when I started up again the popup dialogs are often missing the text, as are the buttons to click. Of particular issue is that the mission objectives screen has a missing chunk of text in it. This puts a serious crimp into playabili...