just an additional note on what I meant with 'clipboard not working' with kwin 
(from kde4):
it is not that the clipboerd itself is not working (it does, in fact) but it 
is copy/paste via shortcut:
the usual keypress 'alt+print' normally copys screen content to clipboard, 
which can then be pasted in other applications.
with kwin, this gives an error when trying to paste, something like 'the 
application which copied to clipboard has been closed'
so I'm pretty sure this has something to do with kwin.

Werner