Very late answer, but this thread comes up when searching on google for this error message, so I want to give an answer for people having the same issue:
In my case, this error happened due to a severe miscalibration of the trigger. To fix this, you need to boot in service mode (set the jumper on the CPU board) and run the trigger calibration routine. You need some function/signal generator capable of generating a 6 Vp-p sine at 100 Hz (if I remember correctly) for this. Once this has finished properly, the error should disappear.