VNAV Alternate choice.

Hello,I will try to explain my problem really clearly.From now six months, I fly with the 737 family with a really great pleasure. I bought the 747 too and I'm so pleased to play with both those planes.My current problem is with VNAV cruise.PMDG 737 Next Gen have an option in his configuration editor wich allow to use the VNAV ALT, wich allow to not have VNAV disconnecting when you modify your altitude on the MCP and allow you to set this altitude independently, but the FMC still manage speed limitation and other things.This mode is normal one on the 747.For an unknown reason, the FMC won't do that anymore from about a week. So do you have any idea on what can cause this ? FSUIPC 3.70 ? New AIRACS, a wrong SID/STAR approach file ? Or something I missed anywhere ?I checked the options and it stay checked... I checked the .ini file and it's correct : VNAVALT=1Do you know what's happened ans why it don't work anymore ? Is there any registry entry wich avoid me using it ? Thank you for your answer.EDIT // Maybe this is related to the livery ? Maybe each livery have is own way to allow or not this mode ? I tried another kind of 737 last time... I finally get back my VNAV Alt one time with the All NIppon Airline...// EDITFran