[Mark McLeod]

Only the obvious causes:
--When the OI radio is swapped with the RC radio, i.e., the OI radio gets mounted on the robot instead of the RC radio.
--When the team number doesn't match on the OI and RC, but tethering them first so the RC can learn the OI set team number avoids that and it sounds like you tried that.
--Really, really poor radio antenna placement or a disconnected antenna broken inside the housing, but that'd feel loose.
--Low battery or power on either the RC or OI, but the OI power supply and a charged robot battery avoids that.
--Serial cable connections loose or bad or one of the cables has gone bad. Try replacing the two cables connecting the radios.
--Another set of radios broadcasting on the same channel, but changing channels would have tested this.
--Master Code v13 or higher

If you have your older 2007 robot with the same radios you can try communicating with the radios used for that to see if you can isolate the problem to the robot or the OI radio.