I have had this issue many times. Sometimes I am able to undo whatever instigated it by hitting Ctrl + Z on my desktop. But that didn't always work. After a while I figured out that you have to right click on the file or folder, go to "Properties". Then on the "General" tab, click "Advanced". When the advanced settings window pops up, you will need to uncheck the box marked "Folder/File is ready for archiving".
That should do the trick. It has worked for me.