Were you able to resolve this?
It sounds a bit concerning.
I haven't yet updated from original Witcher 3, I've been waiting for things to stabilise, but the idea that my save games may not be compatible is a bit alarming!
1.32 save are compatibile with any NG 4.0x update.
Save made in NG 4.0x update are not compatible with 1.32 update.
OP problem is not incompatible save, he has some mods installed that causing crash. You need to delete or disable all mods that you have installed, you can do it with help of Mod Menager or best way is to simple uinstall game, delete whole game instalation folder manually (to make sure that non files left there) and install NG. Only after this you could install mods but only thoes that are compatible with 4.03 update (you have to check in mod description or test one bay one )
cause of crash also may be:
~ Incorrect user.settings files in the <ur documents>/the Witcher 3 folder (you need to delete all user.settings), or insufficient system privileges to run the game exe or to save game settings files in the documents folder. Running the game exe as an administrator may help with this issue.
~ Outdated or incorrect graphic drivers, lack of directX update: https://www.microsoft.com/en-us/download/details.aspx?id=35
or visual c++ redistrib update (start install_all.bat as administrator): https://www.techpowerup.com/download/visual-c-redistributable-runtime-package-all-in-one
no Net. Framework update, XNA framework or windows is not updated.