Mozilla Crash Report

I don't know guys if you have the same problem like what I just experience a while ago. I was in the middle of updating one of my blogs and then all the windows in my pc were gone. There was a message that appeared on my screen where I made a screen shot of it. I am only wondering why this happens sometimes in my computer. I am not a computer expert which makes me afraid that I can't anymore open my pc. Any idea from the experts why this happen? Thanks in advance. Here is the screen shot I made.