Please confirm you are using IE & connecting via IP (or using another method in which there would be a certificate mismatch, such as shortname or internal DNS name that is not on the certificate). If yes, that is an expected error due to restrictions in IE that does not automatically send cookies for untrusted sites [sporadically]; you will need to close that pop-up and open it again; it _should_ allow the cookie to be sent that will let you select the groups.