ipfilter 4.1.31 - Centos Linux 5.2

Hi,

I have gotten 4.1.31 to compile an run on centos 5.2 linux kernel 2.6.18-92.1.10.el5.

It seems to be mostly working ok after some minor changes for locking. I have just discovered a 
problem with ipnat though trying to setup a ftp proxy rule.

map eth1 192.168.4.0/24  -> 2.2.2.1/32 proxy port ftp ftp/tcp

when I try to insert this I get:
[root@Z1234 proc]# ipnat -CF -f /etc/ipnat.cfg
0 entries flushed from NAT table
0 entries flushed from NAT list
1:ioctl(add/insert nat rule): No such file or directory

other map rules seem to be ok.

Could someone point me where I should start looking for this problem. I haven't been able to
figure out how ip_ftp_pxy.c get compiled and where it ends up. I can't find a .o file in the
Linux/Linux-2.6.18-92.1.10.el5-i686 directory.

Thanks,
Steve