FreeBSD 5.3BETA5 slow network

[Rumen Telbizov]

Dear list,

I've been using FreeBSD 5.3 since BETA2 and
I have this network performance problem.
My network is very slow. I am on a 100Mbit
Lan and when I download a file over it
from the box next to me I achieve speed
of 40KB/s maximum. My previous OS was 4.10
and I did not have this problem. No hardware
change made!

I read UPDATING and tried to set debug.mpsafenet = 0.
Unfortunately it is readonly and cannot be set.
My default value of debug.mpsafenet is 1!

Putting it into loader.conf doesn't do the trick
either. Nor does putting "options NET_WITH_GIANT"
into the kernel.

My system is:
5.3-BETA5 FreeBSD 5.3-BETA5 #3: Mon Sep 20 19:00:21 EEST 2004

Any ideas are welcome.
Thank you in advance.

Rumen Telbizov