Not getting trap name, why ??

I'm using the Net-SNMP Version: 5.2.1.2  (window binary) ,the snmptrapd
application.
 
When I received a trap, I get the trap number (in the example below the
value is 15) instead of the trap name
which should be  "npacInterfaceFailure". I cannot figure out why I
cannot get the name?
 
2005-10-27 16:37:17 NET-SNMP version 5.2.1.2 Started.
2005-10-27 16:37:19 192.168.60.9(via UDP: [192.168.59.9]:-32335) TRAP,
SNMP v1, community hello
 TEKLEC-LSMS-TRAP::teklecLSMSEventsV1 Enterprise Specific Trap (15)
Uptime: 0:48:36.00
 TEKLEC-LSMS-TRAP::eventNbr.0 = INTEGER: 2000
 
My mibs compile Ok , I do not see any errors (verify with debug option
in snmp.conf) when snmptrapd come up.
The mibs files provided with Net-SNMP by default contain the mib
RFC-1215. txt which is used for the trap name. 
 
By trap definition is also OK (see below)
 
npacInterfaceFailure TRAP-TYPE
    ENTERPRISE tekelecLSMSEventsV1
    VARIABLES { eventNbr }
    DESCRIPTION
     "This notification indicates an NPAC interface 
     failure. Its is generated when the ping 
     utility has not receive a response from 
     the interface associated with the NPAC."
    ::= 15
 
thanks
Javier