from VMware KB we read that:
Starting with vSphere 4.1, the Copy and Paste options are, by default, disabled for security reasons.
To be able to copy and paste between the guest operating system and the remote console, you must enable the Copy and Paste options using the vSphere Client.
To enable this option:
1. Log into a vCenter Server system using the vSphere Client and power off the virtual machine.
2. Select the virtual machine, on the Summary tab click Edit Settings.
3. Navigate to Options > Advanced > General and click Configuration Parameters.
4. Click Add Row and type the following values in the Name and Value columns:
isolation.tools.copy.disable – false
isolation.tools.paste.disable – false
NOTE: These options override any settings made in the guest operating system’s VMware Tools control panel.
5. Click OK to close the Configuration Parameters dialog, and click OK again to close the Virtual Machine Properties dialog.
6. Power on the virtual machine.
To enable this option for all the virtual machines in the ESX/ESXi host:
In the ESX/ESXi host, open the /etc/vmware/config file using a text editor.
Add these entries to the file:
Save and close the file. The Copy and Paste options are enabled when the virtual machines restart or resume the next time.