Some of the guys over on Fordmondeo.org are experiencing problems with there ATX also, I've been lucky so far and mine had been hassle free.
Anyway suggestions to resolve your problem are, Change the fluid ( completely ) in the ATx making sure you refill with Ford RECOMMENDED fluid only. Secondly the MLPS could have given up ( MLPS = Manual Lever Position Sensor ) Or perhaps the Micro switch under the O/D button ?
Perhaps contacting Mike_J_C over on Fordmondeo.org would be a good start as heres dealing with a local dealer and Auto Trans specialist.
Hope this helps