More details... From the client log file....
7-29: 16:06:39.476
7-29: 16:06:39.476 My Connections\BigBandTun - Attempting to resolve Hostname (XXX.dyndns.org)
7-29: 16:06:39.486 My Connections\BigBandTun - Initiating IKE Phase 1 (Hostname=XXX.dyndns.org) (IP ADDR=68.221.66.XXX)
7-29: 16:06:39.486 My Connections\BigBandTun - SENDING>>>> ISAKMP OAK MM (SA, VID 2x)
7-29: 16:06:54.558 My Connections\BigBandTun - message not received! Retransmitting!
7-29: 16:06:54.558 My Connections\BigBandTun - SENDING>>>> ISAKMP OAK MM (Retransmission)
7-29: 16:07:09.579 My Connections\BigBandTun - message not received! Retransmitting!
7-29: 16:07:09.579 My Connections\BigBandTun - SENDING>>>> ISAKMP OAK MM (Retransmission)
7-29: 16:07:24.601 My Connections\BigBandTun - message not received! Retransmitting!
7-29: 16:07:24.601 My Connections\BigBandTun - SENDING>>>> ISAKMP OAK MM (Retransmission)
7-29: 16:07:39.623 My Connections\BigBandTun - Exceeded 3 IKE SA negotiation attempts
From the server logfile:
Thur, 07/29/2004 12:06:39 - BBRouter IPsec:Receive Packet address:0x13967d0 from 24.172.56.XXX
Thur, 07/29/2004 12:06:39 - BBRouter IPsec:main_inI1_outR1()
Thur, 07/29/2004 12:06:39 - BBRouter IKE

eer Initialized IKE Main Mode
Thur, 07/29/2004 12:06:39 - BBRouter IKE:main_inI1_outR1() connection not found 68.221.66.XXX[500]-24.172.56.XXX[500]
Thur, 07/29/2004 12:06:39 - BBRouter IKE:Trying Dynamic IP Searching
Thur, 07/29/2004 12:06:39 - BBRouter IPsec:instantiated "BigBandTun_tmp2" for 24.172.56.XXX
Thur, 07/29/2004 12:06:39 - BBRouter IKE:[BigBandTun_tmp2] RX << MM_I1 : 24.172.56.XXX
Thur, 07/29/2004 12:06:39 - BBRouter IPsec:New State index:0, sno:9
Thur, 07/29/2004 12:06:39 - BBRouter IPsec:Oakley Transform 1 accepted
Thur, 07/29/2004 12:06:39 - BBRouter IKE:OAKLEY_PRESHARED_KEY/OAKLEY_3DES_CBC/MODP1024
Thur, 07/29/2004 12:06:39 - BBRouter IKE:[BigBandTun_tmp2] TX >> MM_R1 : 24.172.56.XXX
Thur, 07/29/2004 12:06:39 - BBRouter IPsec:inserting event EVENT_RETRANSMIT, timeout in 10 seconds for #9
Thur, 07/29/2004 12:06:47 - BBRouter IPsec:handling event EVENT_RETRANSMIT for 18ac38aa "BigBandTun_tmp2" #9
Thur, 07/29/2004 12:06:47 - BBRouter IPsec:inserting event EVENT_RETRANSMIT, timeout in 20 seconds for #9
Thur, 07/29/2004 12:06:55 - BBRouter IPsec:Receive Packet address:0x13967d0 from 24.172.56.XXX
Thur, 07/29/2004 12:06:55 - BBRouter IPsec:main_inI1_outR1()
Thur, 07/29/2004 12:06:55 - BBRouter IKE

eer Initialized IKE Main Mode
Thur, 07/29/2004 12:06:55 - BBRouter IKE:[BigBandTun_tmp2] RX << MM_I1 : 24.172.56.XXX
Thur, 07/29/2004 12:06:55 - BBRouter IPsec:New State index:1, sno:10
[It repeated this pattern a couple times, and then finally ended as below]
Thur, 07/29/2004 12:08:17 - BBRouter IPsec:max number of retransmissions (2) reached STATE_MAIN_R1
Thur, 07/29/2004 12:08:33 - BBRouter IPsec:handling event EVENT_RETRANSMIT for 18ac38aa "BigBandTun_tmp2" #12
Thur, 07/29/2004 12:08:33 - BBRouter IPsec:max number of retransmissions (2) reached STATE_MAIN_R1
Thur, 07/29/2004 12:08:33 - BBRouter IPsec:[BigBandTun_tmp2] is removed from the head of conn_list
Thur, 07/29/2004 12:08:33 - BBRouter IPsec:Connection [BigBandTun_tmp2] is deleted from connection table