have You changed anything regarding this assembly?
Have You moved or renamed it, have You changed the folder structure etc. from any of them?
Are there any error messages regarding a missing part?
Can You see them in pathfinder and Your parts are only hidden?
How long since your last reboot? You're using Insight or TC?
Do you have the parts that are not showing up open in another instance of SE?
Each file can only be opened up once by each user.
I don't have them open anywhere. For some reason the parts in the assembly are not being populated in my cache folder. Usually when I open an assembly the cache folder would be populated both with the assembly and part files.