Permission denied to access property 'defaultView' in overlay-parent.js line: 271

We've got a site protected by siteminder -- this is a single signon system.

When a user visits the site & they don't have a special cookie, apache directs them to an external domain to log in... this gives them the cookie. If they have the cookie, they are let in.

If the siteminder session times out and a user accesses something through the overlay, an error is raised in overlay-parent.js (because the iframe is points at an external domain, the logon url).

Error: Permission denied to access property 'defaultView'
Source File: https://example.com/modules/overlay/overlay-parent.js?v=1.0
Line: 271

When this happens, the overlay gets is stuck in a "loading" state and it is not possible to close... the JS stops executing, nothing happens, and the user is left with a broken page.