Copy Account always give an error

Copy Account always give an error

When I attempt to copy an account I get a popup window that asks me to select the resource or resources to copy the account too....I get the below error when I select a resource and hit the arrow to move it to the other box. 

"Number of selected resource cannot exceed 2000. Please try again."

                New to ADManager Plus?

                  New to ADSelfService Plus?