There is a particular case one of our customers ran into where this problem arises. Functionally the core is fine, but in their particular case they were using a 3rd party module that included some malformed Javascript. When the page loads the malformed Javascript, it most likely will invalidate the rest of the Javascript that was loaded for that page. The modal popups in DotNetNuke6 use javascript, so if a page has javascript errors, the popups will not behave as expected.

This is not only particular to the popups, if the page you are loading has malformed javascript, many things may not work as expected.

Check your broswer dev tools to see if there are any javascript errors being thrown.

Hope that helps shed some light.

http://www.dotnetnuke.com/Resources/Forums/forumid/200/threadid/425763/scope/posts.aspx, the same issue with this post but not any workaround.

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