Check that your wall construction is set properly. I believe if the construction is not compatible with an "air" type, eQuest rejects and resets the selection. You can either pull the default Air Wall construction from the library, or change the current construction to a U-Value input rather than a Layered input (assuming this construction isn't used in other walls) and change the U-Value to a minimum of 2.7.

Hope that helps,

Eric