I had this problem today. Couldn't drag and drop any compatible videos from my Win7 folder into my iPad sync area. At first I was getting the unable to play becaue not compatible message, then updated itunes to current version, now it won't even let me execute a drop, gives me the strike out circle mouse icon. These videos were previously sync'd to my ipad, so I know they're compatible. I was able to add them to the iTunes library through the file menu and then move them to the iPad (new iPad). So weird.