Aligning to page or margin bounds in CS5

Duplicating an InDesign page, I found a text frame on the page gets increasingly further to the right on each copy. I thought I’d try another method, and simply align the moved frame to the margin bounds of the page, but I can’t get this to work.

Can anyone make any sense of this entry for ‘align’ in the CS5.5 .sdef?

align‚v : Align page items.
align document
align distribute items page item : The page items to align or distribute.
align option left edges/Œtop edges/Œright edges/Œbottom edges/Œhorizontal centers/Œvertical centers : The type of alignment to apply.
[align distribute bounds item bounds/Œpage bounds/Œmargin bounds/Œspread bounds] : The bounds within which to align or distribute the page items.

I’m not sure why the duplicates move the frames to the right, but here’s my script:

tell theReplicant -- this a document previously created in the script
		-- Adverts first
		set advertPage to make new page
		set advertPage to page 3 -- select the new page (is this required?)
		set applied master of advertPage to master spread "C-Blank Page" -- assign the page
		tell advertPage
			set ruler origin of view preferences of theReplicant to page origin -- check the ruler origin
			set advertFrame to make text frame with properties {geometric bounds:{"10.5mm", "14mm", "183.47mm", "129mm"}, label:"adFrame"} -- create the frame
			tell advertFrame -- stick in the contents
				set contents of insertion point 1 to "[ADVERT PAGE]"
				tell paragraphs
					set justification to center align
					set align to baseline to false
					set applied font to "Arial Black"
					set fill color to "EBG Red"
					set point size to "64pt"
				end tell
				set vertical justification of text frame preferences to center align
			end tell
		end tell
	end tell

Can anyone help – either in stopping the unwanted creeping to the right, or in making the align to margins work?