PackagingResults:Error: Error Unknown Cook Failure

I try to make simple game with cars and multiplayer, but when i try to package it give me this error “PackagingResults:Error: Error Unknown Cook Failure”
Can you help me to fix this?link text

Well, looking to your log I have found this:
Error Wrong class to spawn ‘None’ in Construct Object from Class from Source: /Game/Untitled.Untitled:PersistentLevel.Untitled

Can you check if there is any blueprint (even level ones) trying to spawn ‘None’?

The reason is your blueprint has compile errors, you need to fix the blueprint compile errors first.