Opening Port for RDP on Draytek Router

I seem to be going round in circles - Any help appreciated....

We've been trying to Open a Port (3389) to allow RDP access (from a
defined IP Address). WE've tried this on both a Draytek V2200USB and a
V2600VG but come up with the same (non-)result.

We have static IP address setup in the Router. Downstream it is
connected directly a DSL service. Upstream is is connected to a PC
Server (SBS), where the IP Address is 192.168.1.251. The router itself
is setup as 192.168.1.253.

We've used NAT Setup to Open Port as RDP 192.168.1.251 TCP 3389 3389
(and it is Enabled)

We've also setup Port Redirection as RDP TCP 3389 192.168.1.251 3389
(and it is Active).

However, when we test access with ShieldsUp! this port is totally
Stealth.

We've also tried switching on Remote Management and ShieldsUp!
immediately finds the management Ports open.

So what are we doing wrong? Is there some other settings we need to
change to Open Port 3389.

Any help much appreciated

JohnK

p.s. We have double checked that our ISP is not blocking access, and
they assure us they aren't and opening Remote Management seems to
confirm this.

p.p.s. This has been posted in the Draytek Forum, and discussed with
their expensive Support Helpline to no avail. In addition I've found
other threads from people with a similar problem but these never seem
to come to conclusion.

Any help or similar experience would be very much welcomed

Got it fixed - It was a conflict in the Router AND a setup problem on
the Server.

JohnK