I am having the same problem as documented here: https://tri.be/support/forums/topic/month-navigation-links-not-working/. I am using Woothemes Canvas. It was working fine until the last update and my header.php file is formatted just as you noted in your fix and that is not changing the behavior of the next event links on my calendar pages. If you look at the link that the page is loading, it is not paging, just reloading the same upcoming page.
I am using the latest version of my themes, WordPress and of the EC and EC Pro, and all of my other addons.
I am going to do a test on my beta site and see if I can isolate this by reverting to another theme and by deactivating a couple of new plugins that I am experimenting with.
John