obsd 4.6 on Netra X1

Hello all,
I am running OpenBSD 4.6 on a Netra X1 as a layer2 firewall.  The problem I
seem to be experiencing is that every time the NIC gets saturated (100Mb) i
get the following error on the console twice followed by a kernel panic and
core dump.

dc0: watchdog timeout

As long as I don't max out the network port (i.e 11MBps) everything works as
expected. Is there a bug or am I doing something wrong?  thank you in
advance.

cheers,
abs