Slow network speed with Xen 3.2-1

[virtualroot <virtualroot@gmail.com>]

I'm getting a slow network speed (download/upload) domU and dom0
limits in 10kbps/20kbps.
Booting a kernel without Xen, this doesnt happens

/etc/xen/xend-config.sxp
(network-script network-bridge)
(vif-script vif-bridge)
(dom0-min-mem 196)
(dom0-cpus 0)

cat /etc/xen/XXX.cfg
kernel      = '/boot/vmlinuz-2.6.26-1-xen-amd64'
ramdisk     = '/boot/initrd.img-2.6.26-1-xen-amd64'

memory      = '2048'
vcpus = '4'

root        = '/dev/sda2 ro'
disk        = [
                  'phy:/dev/storage/XXX-disk,sda2,w',
                  'phy:/dev/storage/XXX-swap,sda1,w',
              ]

name        = 'XXX'
vif         = [ 'ip=190.228.X.X,mac=00:16:3E:37:17:9A' ]

root = "/dev/sda2 ro noapic acpi=off nopcmcia noagp nobluetooth"
extra = "3 xencons=tty"

on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'

I use Debian 5.0.2 kernel 2.6.26-1-xen-amd64