I had two Series recordings set up for 8:30 Wed. Via the New Shows page I accidentally set a 3rd timer for that slot (dual tuner PVR).
Later on I checked and it seems that the system had accepted the New Show timer but marked the existing Series (Puberty Blues) as being in error. Yellow exclamation mark.
I cancelled the New Show timer but nothing would let me 'reset' Puberty Blues. I had to cancel that instance and manually set it as a one off recording.
The show was days away from when I was doing this.