Font Size Question

[phusion]

I'm having a problem with my font size. In gnome-control-center, I've
set the font preferences to Arial 10, and font rendering to sub-pixel
smoothing. When I log into X-Windows, the font size is bigger, so then
I go into gnome-control-center, and then single-click on font and the
font suddenly shrinks probably to 10. How can I make the font size
stay permanent? Thanks.