New FMC problem

I have been flying the A330 with great pleasure for some time, and I have never encountered a problem with programming the FMC. However, recently I have come across a problem which has virtually rendered the plane unusable. No matter in which order I input the data, even if I input the flight plan first, as soon as I enter the cruise flight level the error message CRZ FL TOO HIGH appears. It doesn't make any difference whatever altitude I enter, it doesn't make any difference what Cost Index is entered. As a result, the FMC will not make any speed or altitude calculations thus making managed flight an impossibilty. I have searched through the forums and watched various tutorials on You Tube, but I am no nearer solving this problem. It seems strange that this issue has only just reared its ugly head. The only recent change I have made is the updating of nav data to AIRAC 1610. (Incidentally, I did notice when programming the approach to EDDB that the FMC came up with waypoints that don't appear on my charts and wouldn't recognise some that do !) Needless to say, I would appreciate any suggestions that might cure the problem and allow me to use the plane again.