Comment 15 for bug 127749

I think this is probably related:
I'm currently using Ubuntu 9.04, with kernel 2.6.28-11-generic #42-Ubuntu SMP x86-64.
Some programs have problems with UDP checksums, and others don't. When analyzing traffic with wireshark, all of the packets sent from any of the affected programs show up as having a bad checksum, no matter
2 programs that I've noticed specifically that have this problem is a java application that uses java.net to send udp packets, and netcat. For these programs it happens no matter which interface I send the packet out on (ath0, eth0, or loopback). However, if I unplug my network card, everything works as expected.

I'm having absolutely no problem using other udp programs (DNS, etc work fine). netcat works fine in tcp, but not udp. sendip works for udp, but I think it is possible sendip computes the checksums itself.

Relavent line from lspci:
00:19.0 Ethernet controller: Intel Corporation 82566MC Gigabit Network Connection (rev 03)