For the past week now, I have encountered an error with my 160×600 Adsense ad unit. As you can see from the screen shot below, the top ad is missing. In its place is a dot. My guess is that the dot is suppose to be one of those new link unit image that Google has been testing. For whatever reason, Adsense can't find a relevant link unit image, so it displays a dot instead. I sent an email to Adsense support about the problem and they told me it was just an error and they don't think I will see the error again. That was two days ago and I still see the dot. It only happens once in a while, but it happens enough to annoy me. Is anyone else experiencing this problem?