m0n0wall version 1.22

WAN -->m0n0-->Centos-->LAN
WiFi   ------^

I've been attempting to get an Apple Mac (OS X, 10.4.8), when connected 
to WiFi, to VPN through Centos to the LAN. Ultimately, I would like to 
extend this to allow roaming attachments through WAN as well.

However, all appears to work OK 
(STATE_MAIN_R1->STATE_MAIN_R2->STATE_MAIN_R3 & 
STATE_QUICK_R0->STATE_QUICK_R1->STATE_QUICK_R3) with IPsec established, 
but then it halts and ultimately deletes the connection. Inspecting the 
m0n0 log afterwards shows the following:

sis0 @100:2 b 192.168.168.100 -> 10.100.1.199 PR icmp len 20 116 icmp 
unreach/port for 10.100.1.199,51718 - 192.168.168.100,1701 PR udp len 20 
68 K-S IN

I checked 10.100.1.199 and UDP port 51718 is open. I can also ping 
10.100.1.199 from 192.168.168.100 as well. The rule that causes this log 
entry is one that allows ALL traffic, which is why I'm a little confused 
as to why it is getting blocked. Oh yes, and all the firewalls have 
effectively been turned off, only logging remains.

Am I doing something wrong? Any help appreciated.

TIA