When reloading the nameserver, error messages similar to this appears in the system log file:
Apr 5 19:45:24 host named[6556]: domain.com has CNAME and other data (invalid)
Apr 5 19:45:24 host named[6556]: domain.com.hosts:13:domain.com: CNAME and OTHER data error
Apr 5 19:45:24 host named[6556]: master zone "domain.com" (IN) rejected due to errors (serial ####)