This is a bug in Max 2017. I believe it's fixed in 2018. An Autodesk developer wrote this script for me to get the layers back. Place the script in the startup scripts folder, and then restart 3ds Max. Then open your organized file. Everytime you open a file it will make sure that all layers/objects are working.
layer = LayerManager.newLayer()<br>for n in (selection as array) do layer.addnode n script above seems to be a workaround for getting objects back into a layer, but i suspect all my carefully organised layers have gone to bollocks. Wonderful.
Looks like Dictionary was introduced in Max 2017.1. The best you could do is install 2017, update it, use this startup script there, and then Save As 2016 format. To keep working in 2016. Sorry. http://help.autodesk.com/view/3DSMAX/2018/ENU/?guid=__files_GUID_39A9FDB8_E508_413F_BF58_EC8F52BE7CA9_htm
I just had this same exact horrible thing happen with 2018.4 Update. THANKFULLY I stumbled on this thread and found the scrip from monster. That fixed it and all is well again! Thank You to monster!!