Belkin DSL Modem Router Port Forwarding

I have replaced my Netgear wireless router with Belkin FD 2401 v1 (Wirelss modem router), I think it is worth bit over $60 on Ebay off the top of my head. It is overall more stable and reliable, so far so good.

While setting its port forwarding feature (Firewall > Virtual Servers), I noticed if the inbound port is a well known port number (0 - 1024) then it simply doesn't work i.e. no access.

However, any port outside this range (including registered ports) functions well - as shown in the examples beneath:

P.S. the Belkin is running on firmware 1.00.38(Jul 1 2010 13:40:12).