I realise that this problem smacks of corruption and therefore a reinstall might be necessary.

 

My speed tape on the ND shows the red indications well above stall speed, and do not 'decrease' as flap is added.  Indeed it seems to be stuck.  If this is finger trouble on my part, then I would be grateful for suggestions.  It is unneerving having all indications wrong on approach, and with the speed marker flashing yellow then red as more flap is added.  Yet the plane lands at the correct indicated speed.  

 

Otherwise I shall reinstall.

All I can suggest is that maybe the weight wasn't set correctly in the FMC.

You are correct, thanks.  I have found that if a saved panel state is used the content seems to linger on for other flights.  Therefore the GW is filled with that number, and I wasn't bright enough to replace ti with the correct value for the next flight.  Indeed there almost appeared to be an accumulation of successive gross weights until the stall values reached up to meet the upper red dots.

Finger trouble but now sorted.  Again thanks.

Double check your pitot static system as well. Chances are if there is wrong or erroneous indications on the PFD, then its possible you have a pitot system failure or blockage.