For background, I am using ArcGIS 10 with a Desktop ArcInfo concurrent license and ArcGIS Server with a single use license. I have used ArcGIS 9.3.1 in the past and successfully worked with GML data in ArcCatalog and also in a ArcGIS Server based component I wrote.
While working with GML sourced from ArcGIS 10 Server's WFS service extension and ArcCatalog/ArcMap 10, it seems GML cannot be read. The GML I have produced shows "No Geometry" when browsed in ArcCatalog, though I can load the same GML file into Gaia with no issues.
I have installed the Data Interoperopability Extension, but I do not have a license for Data Interoperability Extension. However, I have tried installing a trail version of Desktop and then installing the Data Interop Extension, and authorizing both with a trial authorization key. The result is the same: "No Geometry". I was hoping a authorized copy of the extension would allow me to work with GML, but it is looking doubtful.