Home Network with Powerline adapters, wireless router and Wireless Access point

the wrt54g- and many other routers will work in client mode IF you have third party firmware - such as dd-wrt which mostly works on the GL and older builds.My suggestion is pick a router firmware distro such as openwrt or ddwrt, look at its feature list, then pick a router they support- since not every router will do what you want.

1) For some reason the belkin powerline adapters don't like carrying wireless-originating signals. Could this be possible?

No. This is not possible, at least not the way you asked the question. Powerline adapters try to come as close as is reasonable given their limitations to being a substitute for a length of Cat 5e ethernet cable. They would not care about the source of the ethernet packets they are exchanging. Indeed, I can not think of a way they could detect where a packet originated.

If you've done a simple verification test by directly connecting a computer to each powerline adapter to verify they can talk to each other then I would not suspect the powerline ethernet adapters.

A BTW which is not connected to your problem: You did enable the security on these adapters, yes? Also, it might possibly be helpful if you included the model number of your Belkin powerline adapters so people could look at their specs.

2) The primary Cisco ADSL router doesn't want to communicate with other devices on my network more than one hop away from it. I'm making an assumption here that within the Netgear box the wireless and wired sides are handled differently. Could this be true?

While as Hello71 suggested in his comment, some routers can filter wired and wireless traffic differently, I doubt this is the default behavior. So unless you have configured your router's behavior to limit connectivity, this is not the first place I would look.

Since what you are trying to do is add another Wireless Access Point to your existing network perhaps this guide on how to add a WAP to a LAN might be helpful to you. I believe the guide's network diagram matches the gist of what you are trying to do, no?

Update To Try to Figure Out What Works & What Does Not Work

Anthony, I'm afraid I may be lost. For this edit I'm mostly trying to get in synch. I discarded a lot of the questions I asked earlier because they no longer seemed pertinent. Also, the questions are repeated & answered in your comments below.

I kept the text diagram (below). It was also edited both to update it based on your comments and to correct a (stupid) mistake I noticed.

( Internet )
    |
 ( ISP )
    |
 [Cisco 877W ADSL modem]
    |
  ?.?.?.?  (external IP from ISP's DHCP)
 [Cisco 877W router] (NAT device, LAN DHCP: 192.168.x.11 to .254)
  192.168.x.1 (877W's fixed internal LAN IP)
    |___________________________________|
       |                           |
       |                           |
    [Belkin F5D4076]               |
      /|\                       [ PC1 ] 192.168.x.111
   powerline
      \|/
    [Belkin F5D4076]
       |
       |
 [Netgear DG834G v3 (4.01.40)] (WAP, NAT & DHCP disabled)
  192.168.x.5 (fixed LAN IP)
    |___________________________________|
       |                           :
       |                         Wi-Fi
       |                           :
    [ PC2 ] 192.168.x.112       [ PC3 ] 192.168.x.113

Here's where I think we're at with adding another WAP to your LAN.

1. When you connect your Netgear DG834G v3 as shown in the diagram above, then you have wired LAN & WAN connectivity to the DG834G. But you are unable to access the LAN when using the wireless in the DG834G.

2. When you substitute a Netgear WPN802 v1 for the DG834G and use the same configuration as above then you are able to connect to both LAN & WAN using both wired & wireless connections to the WPN802.

3. Wireless access using the Cisco 877W works correctly.

4. In the DG834G's Wireless Settings section you have

   • Enable Wireless Access Point enabled/checked.
   • Allow Broadcast Name (SSID) enabled/checked.
   • Wireless Isolation disabled/unchecked.

I hope the above is a correct summary.

If it is, then the remaining unanswered part of you question seems to me to be why you can't get wireless to work when using the DG834G. After all, the whole point of this was to use the DG834G as a WAP, no?

Beats the heck out of me.

But if the network configuration above allows wireless to "work" when using the WPN802 then it should also work when using the DG834G. It's just a matter of tracking down what it is about the DG834G that is keeping wireless from working for you.

Does your DG834G configuration have an Advanced Wireless Settings section? If it does make sure that WDS Mode, Enable Wireless Bridging & Repeating is not enabled/checked.

A request. If you have an update that is longer than a sentence or two, please add it by updating your original question. The comments section is not really well suited to or meant for an extended discussion. :-)

Update responding to FINAL RESOLUTION of sorts:

I now have the original DG834Gv3 running both wirelessly and wired, and both wired devices and wireless devices get internet connectivity.

&deity. be praised!!

The only anomaly is the powerbook which I've had to keep wired, as no matter what I do it refuses to work wirelessly.

It should work. I suggest either asking a new question here or trying another PowerPC Mac related discussion board. FWIW, you might try asking about this on the G-Group.

I still have suspicions that the 877W isn't quite right; I'm fairly sure that if I RJ45 the powerline adapter into a different LAN port on it then everything will break.

I don't see how this could happen. All the LAN ports on the 877W should be equivalent from a network access perspective. But at this point I can understand you reluctance to change anything.