Huge number of "Bad_IP_Checksum" warnings on FreeBSD8 captured traffic.

I have not counted but nearly every packet captured through tcpdump on FreeBSD 8 i386 when analyzed by Bro
generates a “Bad IP Checksum” weird warning.This only happens to me on FreeBSD and I run a lot of systems:
Windows7,MacOSX,Linuxes,Solaris…
So,how can I avoid this and filter only the normal warnings,because it seems very related to FreeBSD 8 network
interfaces,tcpdump on FreeBSD 8 ,etc.

Thanks.

Is your interface doing TCP offloading? Try running Bro with the "-C" flag.

   .Seth