Poor TCP performance over WAN with out-of-order packets

Hi!

I have the next problem:

We have a 12 Mibt/s WAN. The delay is 40ms. There are out-of-order packets,
from 10 packet come back 3 in incorrect order.

Because of this, between two Windows (Windows XP, 2000 Professional, 2000
Server, or 2003 Server) is the maximum bandwidth 800kbit/s over TCP. It
doesn’t matter, wich protocoll is in application layer (SMB, FTP, SSH,…). In
test environment is the same case, if i set out-of-order packets over the
test connection (with random delay).

Between two Linux isn’t any problem, they use the maximum available
bandwith. And the most interesting thing: If the sender is Linux and the
reciever is Windows, isn’t any problem. But if the sender is a Windows
machine, it sends only with 800kbit/s. (Over the WAN, and in the test network
too.)

If i set the "TcpMaxDupAcks" TCP/IP parameter on the sender, the bandwidth
will be 1 – 1,1 Mbit/s, but it is just a little result.

Can somebody help me?

Thank!