That was possible to me about two months ago. But now I can't do any operation with copy-paste using key combinations:
copy or paste within "text"
copy or paste any element
etc.
My operation system is Ubuntu 10.10 (Linux nick 2.6.35-29-generic #51-Ubuntu SMP Fri Apr 15 17:13:54 UTC 2011 i686 GNU/Linux).
Browser - any.Situation with Ctrl+z is the same.