This Magento extension will be discontinued (or 'is' depending on when your read this) starting May 1st 2014.
There will be no support and no updates, I will just leave it here for posterity.
You can use instead the new version: https://github.com/tzyganu/UMC1.9
It is not backwards compatible, so I recommend unsintalling this extension and installing the new version.
All open issues from this extension will be moved (if not fixed) in the new version.