I often find that after I migrate a site from one URL to another the publishing pages retain their reference to the original page layouts. This causes a problem when you try to open the Page Settings page.
I followed the guidance of my friend Travis and used the following query to identify the affected pages. Just create a new Content and Structure Report and enter the following CAML query:
<Where><BeginsWith><FieldRef Name="PublishingPageLayout" /><Value Type="URL">http://oldurl</Value></BeginsWith></Where>
Replace "oldurl" with the URL you are looking for.