page numbers underlined in black

Whilst editing some work I'd done I suddenly found the whole text had been underlined. I managed to sort this but the page numbers remain underlined in black and I can't find a way to clear this. I know I can probably remove all the numbers then put them back but the first two pages of my work are number free and I want them to stay that way. it was too much hassle removing the numbers from those two pages for me to want to do it again!

I'm using Word 2007 with Win7 and my browser is FF. Can anyone give me an easy solution please? Plus a reason for this?
Many thanks.