I'm stumped. My app is up and running locally, and I have an /etc/ hosts entry pointing local.mydomain.com to 127.0.0.1. My configuration at Twitter has my callback at http://local.mydomain.com/auth/complete. My starting point is http://local.mydomain.com/auth/start.
When I run through the process with Firefox, Internet Explorer, or Safari (all on Windows), everything works beautifully. When I try with Opera, I get to the Twitter allow/deny page, and when I click the "Allow" button I can see that the browser briefly does something, but then it doesn't go anywhere. I'm left staring at the allow/deny page. The deny button, though, works fine. This behavior is the same whether I'm already signed into Twitter or not. Looking at my app log, I can plainly see the browser never came back to my /auth/complete method, it stayed with Twitter. But when I run through authentication using Opera with any of the live demo apps listed at http://apiwiki.twitter.com/OAuth-Examples, they work fine. Why the heck would the allow button not work only with my app and only with Opera? I've tried clearing out all caches and cookies and nothing has made a difference. I'm grasping at straws here. Anybody got one?
