I am having a similar problem - it appears that the Esri Open connection to WFS does not send the spatial reference system information. It's almost as if that has been disabled. the connection appears to read the service, I can select the features, and when I try to preview the service it seems to be indexing, but then there is no geometry and nothing in the tables.
Is there a way to force Arc to send the SRS information to a WFS Service?