I’m not referring to the type of zoning that involves designating what type of development is permitted on tracts of land, although that’s a pretty good analogy for the error we saw in both SharePoint 2007 and SharePoint 2010 during the process of testing and validating an upgrade.
The Error: "Customization has been disabled for this zone"
When we attempted to apply a page layout to an existing page or change the page layout of a new page, we got the error "Customization has been disabled for this zone." Since we have a lot of customizations going on (master page, CSS, page layouts and web parts), the first thing we did was to isolate the issue since all of those pieces are so closely tied together. After testing several different combinations, we knew that the master page and CSS were not the issue. And, when we used default Out-Of-The-Box page layouts, we could not re-create the error.
The Problem: Custom page layouts included web part zones that did not allow customizations or personalization
The developer focused on the custom page layouts and found that they included web part zones that did not allow customizations:
The Resolution: Remove the customization and personalization attributes
The attributes AllowCustomization="False" and AllowPersonalization="False" were removed and the problem was resolved.