Sitting down to work on the IFO, I couldn't lock the Yarm.  I looked at the error signal as well as the transmission on Dataviewer, as usual, and saw that the POY error signal was almost non-existant. 

Since there was work on the POY table today (Steve removed the oplev test setup, elog 10489 and Q centered the SRM oplev after doing SRMI alignment, no elog yet), I went out to have a look at the table. 

There was nothing occluding the POY beam, which I traced back to the edge of the table.  The beam looked nice and round, so I decided that wasn't it.  I jiggled the PD cables, and lo and behold, the POY RF out cable almost came off in my hand it was so loose.  My suspicion is that whomever was the last to put the POY RF out back didn't tighten the cable and then the work today jiggled the cable loose.  I tightened the cable, and by the time I was back to the control room the arm was locked and Koji was already running the alignment scripts.