First, thank you for your plugin, as it works very well.
But, as a plugin'developer too, I might have found an issue in your oAuth process. Let me explain:
I try to figure out why a function in your plugin intercept a callback from mine. I think, it's because you have written this in your code:
which call top_authorize function on admin initialisation, even for other plugins.
This function will check for oauth_token in the request part of the url and change the url for another which contain "page=TweetOldPost". And of course, all callbacks from Twitter oAuth have a "oauth_token" parameter...
By deactivating your plugin, I was able to authenticate on my own plugin. And each time I reactivate your plugin, it does the same thing.
So could you try to use an other way to manage your anthentication so it won't interfere with other plugins using oauth?
Thanks, and let me know if I can help.
PS: my oauth plugin is not available yet on wordpress.org as it is in internal beta testing phase.