No, not a problem with IPv6 as that is not necessary to get a working ip address under IPv4, as you'd like to do. Turning IPv6 off may even help, ya. Things that come to mind are:
-are you choosing a unique ip address? one other than any other machines or devices on the network?
-disable the DHCP server on router completely. Not needed (if all devices on network will be setup static.)
-make sure the are no unnecessary restrictive settings in the router. An example would be the built in firewall preventing the ip address you are choosing, as in it's blocking a range.
-make sure that if mac address is checked and verified by the router, that your nic card (or onboard lan) is included to be allowed
Basically, if it isn't working for you, the router is most likely preventing it for one reason or another.
Britgeezer: Glad it's working for you.
You could add the dns server that your ISP provides as the alternate entry, but that is unnecessary to do.