Taken from this article.
Recently I found it impossible to use cut and past from any java app. Turns out this is a security setting which is turned off by default.
C:\Program Files (x86)\Java\jre6\lib\security
And edit a file called java.policy
Add this line just below
// "standard" properies that can be read by anyone permission java.awt.AWTPermission "accessClipboard";
Save the file to your desktop and cut and past it back into the folder (windows prevents programs not running as admin to save or overwrite files in that directory)
Restart the app, it should work now.