Ensure no inteference from cordless phone base stations (need to unplug from wall to check) microwaves, TV's etc beside router. Are the wireless LAN and internet indicator lights on and steady - i.e. not flashing? Try changing microfilters (borrow one if necessary.) Check your phone line for background noise using a corded phone in the main socket (where your router should be - not an extension socket.) as noise on the line can prevent synchronisation of router and lights keep flashing. Last thing to do is buy a new router.