Transferring to wrong page

I though't I'd got past this sort of thing but obviously not!
Does anyone know why using Response.Redirect("page.aspx") and/or Server.Transfer("page.aspx") are moving to the wrong page?
I have a very simple setup where a User makes a selection on page 1, clicks the Next button and makes a selection on the next page (and so on...).  The problem is, after moving to the second page, no matter what I do, the Next button redirects (or transfers) back to the first page and not the third one.
I have to be honest, it's driving me nuts so any help would be greatly appreciated.
Chris.
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