pvm connection problems

[Vittorio]

At office I'm trying to solve a heavy statistical problem by means of 
parallel computation with R and pvm.
The problem is with setting up the 
cluster of computers which - to begin with - is made of two pentium 4 
with freebsd 5.4 (host uffbsd) and 6.0 (host NbBSD). 

They see each 
other. From NbBSD:

# ping uffbsd
PING uffbsd.grtn.prv 
(10.155.194.115): 56 data bytes
64 bytes from 10.155.194.115: 
icmp_seq=0 ttl=64 time=0.221 ms
64 bytes from 10.155.194.115: 
icmp_seq=1 ttl=64 time=0.193 ms

But trying to setup the virtual 
machine 

pvm> add NbBSD
add NbBSD
0 successful
                    
HOST     DTID
                   NbBSD Duplicate host
pvm> conf
conf
1 
host, 1 data format
                    HOST     DTID     ARCH   
SPEED       DSIG
          NbBSD.myd.prv    40000  FREEBSD    1000 
0x00408841
pvm> add uffbsd
add uffbsd
0 successful
                    
HOST     DTID
                  uffbsd Can't start pvmd

Auto-
Diagnosing Failed Hosts...
uffbsd...
Verifying Local Path to "rsh"...
Rsh found in /usr/bin/rsh - O.K.
Testing Rsh/Rhosts Access to Host 
"uffbsd"...

Rsh/Rhosts Access FAILED - "uffbsd.myd.prv: Connection 
refused"
Make sure host uffbsd is up and connected to
a network and 
check its DNS / IP address.
Also verify that NbBSD.myd.prv is allowed
rsh access on uffbsd
Add this line to the $HOME/.rhosts on uffbsd:
NbBSD.myd.prv victor
...........................................

Of 
course, in /home/victor/.rhost on uffbsd there's the required line.
The 
same reciprocal situation happens from host uffbsd.

Perhaps I'm 
missing something.
Could you please help me?
Vittorio