I have just got a Vigor 2830n to replace a Vigor 2600G. Throughput from the internet is as expected ~4Mbps but the router admin pages at 192.168.1.1 are very slow like they're coming from a dialup modem. Is that normal?

Slowness is evident on a Windows 7 desktop and Mac iBook so presumably not client-side. It is evident in all browsers but some eg FF handle it better than others.