Netgear + port forwarding

Hi

I have an old DG814 on which I suspect the port forwarding has packed up.
It always took ages to update the display anyway - days sometimes - though the
settings *were* shown in the backup file.

I've also got a DG834v3 and when I try and use that as a replacement, when I add
a service and point it and the appropriate IP i.e. 192.168.0.4 it says "IP
address is not valid" despite the fact it's shown in the "Devices connected
list"

Are all Netgear routers crap at port forwarding and is there a make that I can
rely to do what it's told? I'm happy to use an old wired 4-port unit.

TIA
Andy