The remote control for my Macintosh TV will power up the computer but does not provide any control of the unit after that. The replacement remote has the same symptoms.
To resolve this problem you need to reset the Parameter RAM (PRAM) by holding down the Command, Option, P, and R keys while starting up your computer.
Your Macintosh TV will sound its normal startup chord twice. After the second chord you can release the keys you are holding down. Your remote control should now be functional in controlling your Macintosh TV.