It's a bug. Basically both packages (the "gizmo-installer" package and the "gizmo" package) are trying to provide the same file (/usr/share/icons/hicolor/scalable/hildon/gizmo-project.png).

I was able to get around it by bringing up a shell as root (using gainroot) and then getting rid off the installer with:

And then just choosing to install the main Gizmo package for install through Application Manager.

Actually I think you should be able to just uninstall gizmo-install through Application Manager itself now that I think about it.