No V Speeds, and no Magenta Line

Hi,

When I start up, there is a default Vref shown on the PFDs. When the CDUs and Instr station start up, no magenta line appears on the NDs and No VSpeeds on the PFDs. everything had been ok until this week.

The CDUs are trying to talk to the displays. If I use the CDU to change the range on the ND, it will change momentarily and immediately revert to the selected range, so they are communicating with the displays.

I have run PMFileCheck and no errors - everything checks OK.

But why no speeds or track ??

Many thanks
Ray