Yesterday had this issue of the FMC refusing to update when changing crossing altitudes and/or changing direct to waypoints. At least it didn't lock up the sim as before. I had this issue with the first release but was hoping SP1 had completely eliminated this. Only happened once in 15 flights. New SP1 install. Anyone else seen this with SP1? I fly alot of hours! 20 or 30 a week.

Had the same issue yesterday. I was doing a flight for my VA. SBCF - SBBR - SBFZ. I flew the first leg from SBCF to SBBR, which went normal. Then I made my stop at Brasilia then proceeded to Fortaleza. I didn't notice anything wrong until ATC asked me to change the approach procedure. I tried to select the other procedure in the DEP/ARR page, but the CDU didn't want to update it. I also couldn't change anything in the LEGS page; add/remove waypoints, contraints or anything. Luckly the approach wasn't RNAV, so I had the chance to traing some VOR navigation in the 737. The sim didn't lock or feezed or anything. Just the CDU that wouldn't update. It never happened to me before and the only thing I did different was to make the stopover and fly again in the same session (without exiting the flight). I didn't change anything in the flight also; airplane, time, wheather and anything else.

The next time this happens try the FO's cdu & see if it works.

The next time this happens try the FO's cdu & see if it works.

I did. Wasn't updating too.