Version 1.21.3 is available for download. This is a maintenance release fixing a number of issues and improving validation of Image Sizing settings. This time the autoupdate feature should work without issues. To apply the autoupdate:
  • From Lightroom's main menu, go File > Plug-in Manager
  • Select MobileMe Gallery in the list on the left hand side.
  • Click Check for Updates in the Plug-in Info section on the right.
  • Review the list of changes and click Download Update
  • After the update has been applied, restart Lightroom for the changes to take effect.
This is it! By the way, make sure to check out the FAQ page. I posted my recommendations for Image Sizing settings - the topic that causes frequent confusion.