So I created a new application, updated the keys, and tested things out: worked just as intended.
When logged into <!-- m --><a class="postlink" href="
www.corsulian.com">
www.corsulian.com, I could connect with Facebook without a problem.
I then decided to follow the cross-domain receiver error instructions as well just to make sure that didn't happen.
Now, upon navigating to <!-- m --><a class="postlink" href="
corsulian.com">
corsulian.com, I was expected to be redirected to
www.corsulian.com">
www.corsulian.com. I was not redirected. When I tried connecting by Facebook while still at
corsulian.com">
corsulian.com and that's when the whole "new window with no navigation" weirdness appeared. That was probably always the case but I just never bothered to type "www" for my own site.
I repeated the steps a few times to confirm.
<!-- m --><a class="postlink" href="
www.corsulian.com">
www.corsulian.com works just fine.
<!-- m --><a class="postlink" href="
corsulian.com">
corsulian.com sporadically throws the cross-domain receiver error and, when it doesn't, it opens the site in a new window with no navigation.
It seems the problem may lie somewhere in the redirect - but I compared the two app settings just to make sure and I was surprised to find differences as I had only filled in the minimum things for both:
Deltas:
Profiles tab
Publisher Mode
Old App: Inline
New App: Dialog (Legacy)
Canvas tab
Canvas Callback URL
Old App: <!-- m --><a class="postlink" href="
www.corsulian.com/">
www.corsulian.com/
New App: <!-- m --><a class="postlink" href="
www.corsulian.com">
www.corsulian.com
Advanced tab
Session Secret Whitelist Exception
Old App: Disable
New App: Enable