Haven't seen this message in other browsers, but in IE after I've filled in the popup and I click "save", I get an IE warning that says "Your changes will be lost if you close this popup now." But if I just disregard that warning and click "ok" and then submit the whole node form... everything's fine, no changes are lost, the new noderef content is created and properly referenced.

So basically it's working correctly, but this warning comes up.

So I guess the question is how can that warning be switched off in IE?