The security has been tightened in vSphere 4.1, so that’s why by default if you install vSphere 4.1 or if you upgrade your vSphere 4.0 installation, you can’t copy paste between the VI client and the VMs running in your vSphere environment.  You can read more about why it was changed in vSphere 4.1 in ESX 4.1 configuration guide (page 213). To be able to copy and paste between the guest operating system and the remote console, you must enable the Copy and Paste option.

How to re-enable the copy-paste between VI client and VM in vSphere 4.1 | ESX Virtualization.