about NLANR

Hi
   I used the trace file from NLANR to test Bro. But Bro does nothing but report
bad checksum.
Sessions.cc: Weird("bad_IP_checksum", hdr, pkt);
                        return;
TCP.cc: Weird("bad_TCP_checksum");
                return;

What should I do , to make trace file available to Bro?

Thanks very much!
Have a nice day!
Ciao
Cloud