I have 1 user out of around 150 whose chat windows don't resolve. If you can find the cursor, then you can highlight the text and the text box will resolve enough to communicate. Windows 7 professional, dual monitors. I uninstalled as admin and reinstalled and it worked briefly. Another time I was just playing with it and bouncing it back and forth between the monitors and it worked, but again, only briefly. Image of after some text has been highlighted (image has been altered slightly for anonymity):
You can see that it's holding the background image of when it was opened and after the background image changed, it was still holding the first image. Also, you can see that the only text visible is that which has been highlighted. The remainder is not usable. When I reinstalled it, I installed the latest release. The previous was a few versions behind.