sorry, yeah, should have said that
was weird
i'm not a complete newbie to photoshop, although this will make me sound like one
for some reason the selection was feathering, even though i wasn't setting 'feather', been doing it for ages
i looked in all the obvious places, the most obvious on the tool at the top of the page, but no, could not see why
but today it decides to start working, didn't touch anything, just called a friend, and whilst explaining to him, tested it and it worked
just one of those stupid computer mysteries, must be a bug or something
is working now so will see if it lasts