If you've turned off DHCP on the AP, and you try to connect to it by connecting a PC directly to it, you might have a hard time because your PC won't get an IP address (DHCP turned off). You can work around this by manually assigning your PC an IP address in the same subnet as your AP. For example, if your AP is set as 192.168.1.200, and you connect a PC to it, assign the PC anything in the 192.168.1.X range. From there, you should be able to connect to it.
But if you plug the AP into your regular network, you should be able to connect to it regardless. Besides disabling DHCP and making sure it has it's own unique address, remember that you dont plug it in in the WAN/Internet port, you plug it into the rest of your network on a regular switch/PC port (where you would normally plug a PC into it). If it's plugged into the network and has its own address (which correlates to your network), you should be good.
And you say that when you try to assign it an address, it says it's an 'invalid address'? You might be mistyping something or not following basic network addressing rules. To make sure you know what your subnet mask and default gateway are, run an ipconfig on a windows PC. You can essentially copy these settings, just making sure the IP address is unique. If you copy most of the settings, it should work for you (likely 192.168.1.XXX address, 255.255.255.0 subnet, 192.168.1.1 default gateway). Sometimes (rarely) you might see a router ask for an address in CIDR format. In which case, you have to input it as 192.168.1.X/24 (your network is /24 if your subnetmask is 255.255.255.0). This is pretty rare in home user gear though.
Hope this helps.
Last edited by scotty; 10-24-2008 at 12:06 PM.