In VNAV Path and on descent with the IAS bugging inappropriately to the Up speed just select LVL CHG and have your mate enter a Cruise Altitude of several Hundred feet lower than your current Altitude and execute.
This does solve the problem but I have had to repeat the operation a second time on a couple of occasions.
I will leave the whys and how's to the experts.
I should also add that this will change the descent speed back to a figure that is more appropriate. It may not be exactly 280/250 but you will now be able to ammend this descent speed and execute it.
Hardest part of the problem is convincing other people of the issue without it being discounted as being in an "energy effeciency mode".
I share your pain.
Last edited by ad-astra; 25th Sep 2013 at 21:56.