Network Load Balancing Problem

Hello ,

my name is Fabio ,
 i have a problem with the "fast load balancing solution of
Microsoft".

I have 2 web server (standard edition) in workgroup, wired with two
network card
in two switch (layer 2, not router).

                    DMZ                LAN
Server 1    10.10.10.57    10.10.20.57
Server 2    10.10.10.52    10.10.20.52

With NLB manager in the Server1 i create new cluster

cluster.x.y    10.10.10.60

unicast mode
rules ****t 80 affinity single

Then i add first (local) host ,
when i add the second host i need to use the local admin grants with
this

10.10.10.52\administrator    password

Then all of the host are converged,

In the all IIS admin i create the same site, with same file etc

In the firewall i create the static NAT line for the 10.10.10.60 IP ;
when i try to open the url of my example page
the cluster response only with the second host, if i stopped this
service or i shutdown this second host my
example page don't open.

where is the mistake?

Thanks a lot

Fabio Cecaro