This is driving me nuts!  For several months I've been flying the 757 including programming a flight plan and then the FMC, and everything has worked normally except the swings in the autopilot.   I installed FSUIC 4 and that helped the autopilot problems.  In the last few days I programed a flight plan in Flight Planner, select the 757, install the saved flight plan, then program the CDU. Yesterday I used a saved flight plan, and the CDU told me KABQ was "not in database."  The flight plan never would install, I always got a message saying something to the effect that there was no route installed.  I tried again today with a tried and true route from KRSW to KATL.  The CDU told me KATL wasn't in the database and it wouldn't accept a flight plan.

The only change I've made is to reprogram the autopilot to eliminate the  wild swings reported frequently in another thread.

Any ideas of what's going wrong?