Set up Remote Desktop with iMac (OS 10.6)

[Richard Hein]

Spent a most frustrating night with me remotely attempting assist user
to set up VPN/RDP so it would work. We tried to get his brand new
iMac to connect to his Win 7 64 bit office computer and were never
able.
We could always easily authenticate and establish a VPN connection to
his office network.
When we tried to RDP onto his office computer (using both the most
recent version of Microsoft's software (I think it is version 2.01)
and another program called CoRD (newest version)) the both programs
would try to establish connections and then, after about 15-30
seconds, time out. We were never able to establish a connection to
his desktop.
At one point, I even tried to go from his computer onto a Win XP (SP3)
computer in his office that I could also connect with from my iMac. He
could not connect to that either.
Meanwhile, he is able to log on from the same location and using the
same router from his iPad, I am able to log on with my iMac (OS
version 10.5) and he has also been able to log on in the past with
another iMac that is not now in his home but at another place and not
accessible.
We checked the settings on my iMac (successful at connecting) and his
(unsuccessful) and found that all items except one were identical -
the one different thing was because of the different version of the
OS.
There are two odd things between his and my machines: while having an
active VPN connection on his computer, we were never able to ping
anything on his network. His office computer is at IP address:
192.168.50.39 and he was not able to ping that or any other item in
his office network from his computer. I was able to immediately ping
his computer or any other office IP resource from my iMac while
connected by VPN.
The second difference is that when I ran a port scan for his IP
address from my iMac using the Network Utility while connected to his
office via VPN, I got open TCP ports at 135, 139, 445, 3389 (I think
this is for RDP), 4357, 49152, 49153, 49154, 49172, 49173. When I
scanned from his computer in the same way I got nothing. No ping, not
port scan. I think these are the most relevant facts relating to this
problem. There must be something on his new computer - some obscure
setting - that is causing this problem and which needs to be fixed.
I tried to upgrade the firmware on his router (a BEFSX41, versino
2.1), but was unable to.
The other piece of relevant information is that Saul just bought this
computer and used the firewire sync (I think) program to synchronize
all settings and programs from his old (G5) computer to the new
(Intel) one. We are pretty certain that the problem is with some
obscure setting on his new iMac.
Do you have any thoughts on this?