hey there folks, this is a post from the now working PC! Yay!
we're not completely sure what the problem was but most likely seems to be a conflict between two security programmes. they were installed by different users and had run side by side for a while, but it would seem they finally fell out! anyway, all appears to be fine now, and has been for a few days. i haven't posted earlier as i've been over in Cardiff to see Tigertailz!
thanks for all your comments