logging

Jan 9 06:12:39 kernel: pid 468 (php), uid 0, was killed: out of swap space
Jan 9 06:12:38 kernel: pid 464 (php), uid 0, was killed: out of swap space

System is m0n0wall 1.3 
Hardware Dell GX 350MHz 128MB/ram
NICs 2(3Com 3c905C-TX Fast Etherlink XL) , Intel 82559 Pro/100 Ethernet and
3Com 3c905B-TX Fast Etherlink XL.

I did not see this before, and I looked it up in the forum it was 32 MB ram 
In my scenario it is 128MB and not more than 30 clients. Running Captive
portal on LAN with DHCP and not much traffic shaper rules on WAN> ram usage
did not exceed 40%
If there is any help it will be appreciated.

Best regards,
Mohammed Ismail