NETIO UDP benchmark problem

Hello,
recently i have been testing two servers  via crosslink. Both have
Freebsd installed >

twin1$ uname -a
FreeBSD twin1 8.0-BETA2 FreeBSD 8.0-BETA2 #0: Sun Aug 16
22:57:29 CEST 2009
viktor_at_twin1:/usr/obj/usr/src/sys/GEN_NO_DBG  amd64

twin2$ uname -a
FreeBSD kitt.twin2 8.0-BETA2 FreeBSD 8.0-BETA2 #0: Wed Jul 22 15:05:19
CEST 2009     viktor_at_kitt.twin2:/usr/obj/usr/src/sys/GEN_NO_DBG  amd64

GEN_NO_DBG is GENERIC kernel without debugging options

Twin2 is virtual machine on the same hardware as twin1, vmware used.

I have this set installed on both machines >
twin1$ pkg_info
NetPIPE-3.7.1       A self-scaling network benchmark
gettext-0.17_1      GNU gettext package
gmake-3.81_3        GNU version of 'make' utility
iperf-2.0.4         A tool to measure maximum TCP and UDP bandwidth
libiconv-1.13.1     A character set conversion library
libtool-2.2.6a      Generic shared library support script
netio-1.26          Network benchmark
netperf-2.4.5       Network performance benchmarking package
portaudit-0.5.13    Checks installed ports against a list of security
vulnerabi
portmaster-2.9      Manage your ports without external databases or
languages
screen-4.0.3_6      A multi-screen window manager
ttcp-1.12           Benchmarking tool for analysing TCP and UDP
performance
unzip-5.52_5        List, test and extract compressed files in a ZIP
archive

Both machines are connected via crosslink >
twin1# ifconfig
igb0 : public interface
igb1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=13b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,TSO4>
        ether 00:30:48:c8:f3:91
        inet 10.10.10.10 netmask 0xffffff00 broadcast 10.10.10.255
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active

twin2# ifconfig
em0: public interface
em1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>
        ether 00:0c:29:4b:f1:76
        inet 10.10.10.20 netmask 0xffffff00 broadcast 10.10.10.255
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active

I have set up twin2 as a server for netio >
kitt.twin2# netio -s -p 1122

And then tested from twin1 tcp test >
twin1# netio -p 1122 -t 10.10.10.20

It was allright, i've got some results.

But when I tried UDP, it failed.

The server is still the same >
kitt.twin2# netio -s -p 1122

Client
twin1# netio -p 1122 -u 10.10.10.20

After around 1 minute, twin1 server stopped responding on public
interface, i've been disconnected. Via remote console i could access
the machine, it was acting normally. I could ping both interfaces. I
could even ping from other side of crosslink, from twin2 the privat
interface, but no reply on public interface.
The interface was shown UP in ifconfig, no messages in /var/log/messages.

Then i executed ifconfig igb1 down && ifconfig igb1 up and it worked
again.
I have then executed netio udp test again with 2k udp packets

The server is still the same >
kitt.twin2# netio -s -p 1122

twin1# netio -p 1122 -u -b 2k 10.10.10.20

The same problem on twin1, but now it has crashed the computer >
via remote console i could see this >
twin1# GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12
GET BUF: dmamap load failure - 12

then it executed core dump and restarted.

I am lost, thanks for any advise.

VC