For many months now, pop-up windows have suddenly shown up in the middle of my screen and then disappeared within a fraction of a second. The only thing I'm certain of about these pop-ups is that they happen when I'm running Chrome, and they ONLY affect my 2011 27" iMac running Mountain Lion, not my Macbook. Other than that, the pop-ups seem to happen completely at random. I can be in the middle of editing a document in photoshop when they'll appear and disappear literally in less than half a second. It's pretty annoying to say the least, especially because it de-selects whatever I'm using at the time (like if one showed up while I was typing this out, I would have to click on the text-box before I could continue typing out these words) and I wonder if something may be wrong with my computer. Unfortunately, that's all the information I have about this problem. The pop-ups automatically disappear faster than I can read them, and I have no idea what triggers them. Any help?