Check what the manual page for the underlying semget(2) call on your OS is saying when it's returning ENOSPC. Many systems have a fixed number of semaphore sets (or a fixed overall number of semaphores) that might need to be tweaked by your sysadmin. It may also be that there's existing semaphores lying around that haven't been cleaned up (because something crashed, was sloppy about deallocating them) that you can use the ipcs and ipcrm commands to manually take care of.