It's likely not appreciating being run without user context. That's a not-uncommon problem.
I'm not *sure* DSC is going to prove to be a wonderful software deployment mechanism, at least with the current Windows Installer technology. There are definitely assumptions about the installation environment that don't correspond to the "headless, not necessarily domain joined" world that DSC considers to be its main focus. We need *nix-style packages, really, which is what OneGet is all about.