You are building this in FF, I take it?
I'm not sure the problem, but what seems to be the difference between the pages is the number of page numbers in the class="subHeader".
When it goes beyond 1, that's when the shift occurs.
It could be the number of there are.
You could remove all the and style the links by giving the anchor property 2 or 3px right/left padding. It may help.
BTW, have you seen it in IE6?