Hi COS,
What version of vSphere are you on? It sounds like you're trying to copy/paste from a VM's console view onto your local machine. If I'm understanding wrong please correct me.
I'm not certain but you could try:
1) The standalone VM Remote Console (VMRC) tool, which you install on a Windows or Mac machine. This should have copy/paste from a VM in it: https://my.vmware.com/web/vmware/details?downloadGroup=VMRC70&productId=353
2) Is VM tools installed on your VM? VM tools may be required to make copy/paste work.