LOCK error after creating a clustered index
Follow the How to troubleshoot SQL Server lock related problems and errors steps. 


make sure locks option is 0, see Keep the Locks Configuration Option Default Value
make sure lock escalation disabling trace flags are not in place, see Lock Escalation
check your memory consumption, run DBCC MEMORYSTATUS, see How to use the DBCC MEMORYSTATUS command to monitor memory usage
make sure you do not have open transactions with many locks, see sys.dm_tran_locks and sys.dm_tran_database_transactions


There are millions of tables with clustered indexes out there that do not run into lock exhaustion issues. There is something more at play here.