Apparentely "argument out of range" appears when I add the first Marker on the Map, or when I try to obtain address with the ReverseGeocoder procedure. TTMSFMXWebGMapsReverseGeocoding is on version 1.0.0.0?
Did you enter a correct address, does the content that you add to the marker contain special characters? Unfortunately without more information we are unable to determine what might go wrong in your application, or if it is an issue in our component. We have tested our demo here and are not able to detect any issues.