Lately I have not been able to have more than one Mac at a time communicate properly on my home wifi network.

My setup: A Mac Pro tower using OSX 10.4.11 via Airport Express, and a D-Link wireless router. Little to no problems with getting a signal or using a browser there normally, when no other Mac is in use in the house.

However, I just started using my iBook G4 again in addition. If that and my Mac Pro try to use wifi at the same time, the Mac Pro starts failing to download webpages. (It does still get a wifi signal, though.) This happens with both Firefox and Safari. Tried using a Macbook Pro on the same network; same problem.

All units, laptops and desktops get a wifi signal. Only the Mac Pro loses the ability to surf the web once a laptop is surfing also.

TIA. Any help appreciated.

It sounds like some device is not configured correctly on your WiFi network. Is your WiFi router giving out IP addresses using DHCP? When both of your computers are on the network, what is their IP address? Are they on the same subnet? Do they have routeable IP addresses?

These are things to check, as from what you report, your WiFi router is working correctly.

Yes, my router is giving out IP addresses using DHCP. Haven't been able to check the IP address of my one laptop yet, but my Mac Pro is showing the same IP address as my router. I believe they are all on the same subnet, though.

Question, before I check the IP address on the laptop: Are they supposed to have the same IP address of the router, or different?

All addresses should be different. If the router's is the same as one of your Macs, you've got a problem right there. Just to be sure, you might want to list those IP numbers here.

As alternaut mentioned, each computer should have its own IP address and it should never be the same one as the router. Your network control panel should have the Router IP in the field called router, but each IP address will have a slightly different number, maybe as little as one digit off.

I'll try and set each one with a different IP and see if that works... I always thought the control panel set a different IP automatically...

That's the idea with DHCP. You may want to review the relevant setting(s).

Mine is on DHCP but it reads the same IP as the router setting. Would "Renew DHCP lease" solve that problem?

The IP for your computer should never be the same as the router. The IP address should be the same as the router except for the last octet. The subnet should be the same as the router, and the router IP should appear next in the Network panel.

When you hit renew DHCP Lease, you should get an IP number.

If you are getting the same IP as the router from DHCP, then something is wrong on the router side. It may need to be reconfigured, or simply set back to factory defaults. Your router documentation should explain how to do this, and this is a time to RTDM (read the darn manual).