This week's book giveaways are in the Refactoring and Agile forums. We're giving away four copies each of Re-engineering Legacy Software and Docker in Action and have the authors on-line! See this thread and this one for details.
That would mean, I think, that no ancestor of that element declares a namespace for which DbGML is the prefix. Look in your XML for namespace declarations. And make sure your parser is set up to be namespace-aware (although it probably is).