Status: The AutoTweetNG 4.12 still works in Joomla 1.5. But Facebook, Twitter, and LinkedIn have changed the authorization process; and "1st-movers", the original AutoTweet author, is not longer in the air.
Workarounds: We are not going to publish a new version for Joomla 1.5. In fact, we are launching the new AutoTweet v6.4 (January 2013) with Joomla 3.0 support.
If you need a couple of more months with Joomla 1.5, this is the current way to survive:
1. AutoTweetNG v6.3: Install a testing site with Joomla 2.5 and AutoTweetNG v6.3. Fully configure and test it.