UE4 crashes when opening level or blueprint

My PC froze then i shut down all running processes and restarted UE4. Now i cannot open any blueprint class with my characters skeleton in it. I also cant open any level anymore. How can i resolve this??

logerror says LogLinker: Warning: Can’t find file for asset ‘/Game/backupsk/UE4_Mannequin_Skeleton2_Auto3’ while loading NULL.