Hi everyone, I am encountering a strange problem while using OS X Lion on my 2011 21.5" iMac. Basically, many of the preview icons for my movies files under the folder "Movies" in my dock don't seem to be showing properly, replaced by dotted squares. This sometimes extends to the .pdf and .pages files in the "Documents" folder and even to the files in Finder. Of course, this would seem like an aesthetic problem only, but in reality sometimes I find it difficult to tell whether file x or y in the finder is actually a movie, a document or a folder at first glance because of this! I had the same problem on my 2008 MacBook Pro but I thought that was because of its limited processing power. However, my iMac is brand new and I have around 250GB of free space on my hard drive, so I can't really understand what might be causing this. Hope that you'll be able to help me!