On Sat, 08 Sep 2012 11:54:23 +1000, Obviousman
wrote:

The radar was on, as per the checklist. It was left on in case of an abort.

"How Apollo Flew to the Moon", page 253 says "The program alarms were
caused by a procedureal error that had left the rendezvous radar in a
mode that sent false information to the computer."

It isn't exactly clear to me whether the astronauts made an error
following the procedures, or the list of procedures was wrong. But it
sounds to me like they made an error following the procedures.