I'd try strace'ing the app that is supposed to be receiving them to see if the socket opens are working and what happens with a packet arrives on the port.
No idea what this means. snmptrapd keeps running (strace snmptrapd -f -Le -c /etc/snmp/snmptrapd.conf), but I see this over and over after the initial start:
gettimeofday({1349372532, 120897}, NULL) = 0 gettimeofday({1349372532, 120917}, NULL) = 0 gettimeofday({1349372532, 120934}, NULL) = 0 gettimeofday({1349372532, 120950}, NULL) = 0 select(9, [3 5 7 8], [], [], {5, 0}) = 0 (Timeout) gettimeofday({1349372537, 120615}, NULL) = 0 gettimeofday({1349372537, 120637}, NULL) = 0 gettimeofday({1349372537, 120655}, NULL) = 0 gettimeofday({1349372537, 120670}, NULL) = 0 gettimeofday({1349372537, 120686}, NULL) = 0 gettimeofday({1349372537, 120703}, NULL) = 0 gettimeofday({1349372537, 120721}, NULL) = 0 gettimeofday({1349372537, 120737}, NULL) = 0 select(9, [3 5 7 8], [], [], {5, 0}) = 0 (Timeout) gettimeofday({1349372542, 119701}, NULL) = 0 gettimeofday({1349372542, 119726}, NULL) = 0 gettimeofday({1349372542, 119744}, NULL) = 0 gettimeofday({1349372542, 119760}, NULL) = 0 gettimeofday({1349372542, 119776}, NULL) = 0 gettimeofday({1349372542, 119794}, NULL) = 0 gettimeofday({1349372542, 119813}, NULL) = 0 gettimeofday({1349372542, 119829}, NULL) = 0 select(9, [3 5 7 8], [], [], {5, 0}) = 0 (Timeout) gettimeofday({1349372547, 118753}, NULL) = 0 gettimeofday({1349372547, 118777}, NULL) = 0 gettimeofday({1349372547, 118794}, NULL) = 0 gettimeofday({1349372547, 118811}, NULL) = 0 gettimeofday({1349372547, 118827}, NULL) = 0 gettimeofday({1349372547, 118844}, NULL) = 0 gettimeofday({1349372547, 118862}, NULL) = 0 gettimeofday({1349372547, 118878}, NULL) = 0 select(9, [3 5 7 8], [], [], {0, 1760}) = 0 (Timeout) gettimeofday({1349372547, 120727}, NULL) = 0 gettimeofday({1349372547, 120745}, NULL) = 0 gettimeofday({1349372547, 120761}, NULL) = 0 gettimeofday({1349372547, 120777}, NULL) = 0 gettimeofday({1349372547, 120793}, NULL) = 0 gettimeofday({1349372547, 120809}, NULL) = 0 send(7, "\1\r\0\0\r\0\0\0\0\0\0\0\307\203\225!\0\0\0\0", 20, 0) = 20 gettimeofday({1349372547, 120884}, NULL) = 0 gettimeofday({1349372547, 120908}, NULL) = 0 gettimeofday({1349372547, 120929}, NULL) = 0 select(9, [3 5 7 8], NULL, NULL, {0, 1}) = 1 (in [7], left {0, 1}) getsockname(7, {sa_family=AF_FILE, path=@""}, [2]) = 0 recv(7, "\1\22\0\0\r\0\0\0\0\0\0\0\307\203\225!\10\0\0\0K9\0\0\0\0\0\0", 65536, 0) = 28