I see, thanks for the info. I'll make sure we are tracking this issue.
For additional info, let's discuss how you are using the add-in for this operation. It's my understanding that you are opening the document from the browser or from the add-in's "Open from Office Live" option. Then after editing the doc, you are selecting "Save to Office Live" which results in the dialog appearing without any file name.
If this is correct, then I have a question. Why are you selecting "Save to Office Live" rather than clicking the "Save" button? It is that you want to save the document to a different Workspace, or is it that it wasn't intuitive that clicking "Save" would save the document back to the Workspace? I'm wondering if you thought clicking "Save" would only be for saving the document to the local computer. In fact, clicking "Save" when editing a document in a Workspace will save it back to that Workspace.