I've been having this problem as well, restarting only corrects it for about an hour or so. Was not able to find the library com.apple.finder.plist file in my library and then did a universal search using that string and no results. Not sure why other people have that preference file and I don't. This is a frustrating problem that will influence my decision to purchase new Macs in the future. It's a real time waster. In addition, often when I click on a folder, it comes up empty, even though there may be hundreds of files in the folder. It seems it's part of the same problem, inasmuch as the finder can't process data nodes correctly. The only solution is to open the folder, close it, and open it again and then the files inside it appear, albeit slowly.