help:FreeBSD4.8+IP Filter: v3.4.32,and error:/kernel: in_cksum: out of data by 3

Hi: I have installed the FreeBSD4.8 and IP Filter3.4.32. The FreeBSD BOX is used to NAT. But , i always get the messages "in_cksum: out of data by 3" , And the IP Packets always are droped. How to resolve the problem? the message is: cat /var/log/messages Mar 8 17:13:49 nat /kernel: in

help:FreeBSD4.8+IP Filter: v3.4.32,and error:/kernel: in_cksum: out of data by 3

Hi: I have installed the FreeBSD4.8 and IP Filter3.4.32. The FreeBSD BOX is used to NAT. But , i always get the messages "in_cksum: out of data by 3" , And the IP Packets always are droped. How to resolve the problem? the message is: cat /var/log/messages Mar 8 17:13:49 nat /kernel: in