The situation is remedied (at least mostly) by checking "deselect on copy" and "auto-deselect" the "problem" seems to go away. So yeah, in gvim he got a prompt that said "have to use :w!", but SlickEdit (silently) allowed simply :w to save the selection. Not sure what other options might affect this, but as soon as he hits : the command line adds '<,'> (but that was un-noticed at first) and then the w then I guess operated on the selection. So this may illuminate more of the "problem."
thanks,