nothing is copied that is why the "Paste" is grayed-out or unclickable?
Try to use the keyboard (to see if your "paste" command will work)
Make sure you selected the item you want to copy then press: Ctrl+C
Open the folder where you want to paste the items then press: Ctrl+V
I am using OS Xp, When I used to copy some file there is problem. I right click and click copy, then when go to other folder there is paste botton but can't click.