The router has nothing to do with resolving internal netbios names, between internal machines it's simply a switch.

If netbios names aren't getting resolved then your windows networking is broken. Which machine is acting as your master browser ?

I found it was a badly added rule in the firewall as i reset to factory settings and it worked fine, i started adding all the bits i had set and hey presto i sorted it.

Not sure why an outbounf rule affected it but it did

I'm really not sure either; the router does not do anything to LAN traffic (other than switch it at the Ethernet level if you're using the router's switch). Certainly the firewall has nothing to do with it...so I'm not sure why it works now but I can't imagine what firewall rule you had set that affected it; that doesn't make sense.

It's like saying your wife can't hear you upstairs, but once you changed the front door lock, she could

Its very odd and thats why i couldnt figure out what was causing it. Resolved now so i know what to do if i add a sparious rule in again and it stops working