i believe the ezupgrade extension does not support yet the latest eZ Community Project builds. However, in order to upgrade from 4.4, you can follow these steps, the last two of the only being manual once ezupgrade will support upgrade to 4.5 :
4.4 to 4.5 : http://doc.ez.no/eZ-Publish/Upgrading/Upgrading-to-4.5/Upgrading-from-4.4-to-4.5
4.5 to 2011.5 : http://share.ez.no/download-develop/downloads/ez-publish-community-project-2011.5/upgrading-from-ez-publish-community-project-4.2011-to-2011.5
2011.5 to 2011.6 : http://share.ez.no/download-develop/downloads/ez-publish-community-project-2011.6/upgrading-from-ez-publish-community-project-2011.5-to-2011.6
Let us know how things go, Cheers,
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Nicolas Pastorino
Director Community - eZ
Member of the Community Project Board
