It seems I made a mistake before :(

I pushed a tag to my repository without pushing the corresponding commit. Therefore, the addon's version didn't get updated in the addon.xml file.

I've bumped the version and made sure the commit/tag are there this time.

*addon - plugin.video.academicearth
*version - 1.3.1
*url - git://github.com/jbeluch/xbmc-academic-earth.git
*tag - 1.3.1
*xbmc version - eden

Sorry for the hassle.
Jon