I have a network with a Netgear WDT 624 Router connected Billion modem,
Connected to this is a Toshiba laptop connecting via wireless and a PC via ethernet.
Also visiting laptops connect on occasion. Never had any issues with any of these.

The Mac Pro via the Airport card connects ok via this network to the internet.
The problem is it has trouble seeing others on the network and the others have trouble seeing it.
If with Airport still on and having issues seeing the networked computers, a ethernet cable is connected between it and the router and turned on, the networked computers show up.All is now well.

What I don't understand is that if Airport is now switched off any data being transferred on the network stops and the networked computers disappear. But the Internet is still accessible now via ethernet.

It's almost like the Airport card needs a "boost" by connecting the ethernet cable.

WEP enabled for wireless on the router and all computers have DHCP enabled.

Running out of idea's how to solve this.

Wondering if it's a Leopard issue.

Anyone else having the same problem with wireless?

You updated to 10.5.2 yet? This updated included fixes for some Airport issues.

I would check to see if the airport card has received the proper DNS address from the DHCP.

Perhaps you could shed a little more light by stating what machines you have, which are connecting wirelessly through the AirPort Base Station, and which are connecting with Ethernet through the NetGear Modem.

The post is a tad confusing is all...

Clockwork. My original post kind of sums it up. Probably a bit vague though.
No Airport Base Station only Airport card in the Mac. The Mac and the other computers connect to a Netgear router.

Edited the previous post below to try to make it clearer to understand.
I hope so. Any questions please ask away.

Before adding the Mac Pro to the Network...

I have a network with a Netgear WDT 624 Router connected Billion modem,
Connected to this is a Toshiba laptop connecting via wireless and a PC via ethernet.
Also visiting laptops connect via wireless on occasion. Never had any issues with any of these up to now.

After adding the Mac Pro to the Network

The Mac Pro via the Airport card connects ok via this same network for the internet only.
The problem is seeing others on the network on the Mac and the others have trouble seeing the Mac.
The Toshiba laptop and the PC still see one another ok at this stage.

If with Airport on the Mac still on and having issues seeing the other networked computers, a ethernet cable is connected between it and the router and turned on, the networked computers show up on the Mac and the other computers see it . All is now well.

What I don't understand is that if Airport is now switched off on the Mac any data being transferred on the network stops and the networked computers disappear. But the Internet is still accessible now via ethernet on the Mac.

It's almost like the Airport card on the Mac needs a "boost" by connecting the ethernet cable to it.

WEP enabled for wireless on the router and all computers have DHCP enabled including the Mac.

Summing it up the Mac Pro is the only one having trouble seeing and being seen by the other network computers wirelessly. Unless a ethernet cable from the router is connected to it as well.
It's needing both wireless and ethernet enabled and connected to view the network and Internet for some reason,

I might be reading it wrong but....

You have a wireless netgear router - it connects to the net via a modem. You are connecting the Mac Pro to the modem according to your text - it's not seeing the network, but it is getting internet.

Your use of airport seems to be that you are actually connecting to the netgear via wireless.

When you use ethernet to connect where are you plugging it in? Does your netgear have rules set up?

Could you try turning Airport off before connecting with ethernet and seeing if it works? The issue you may see is that you will have 2 leased IP"s from the router / modem.

Is the modem or the router the wireless source?

I might be reading it wrong but....

You have a wireless netgear router - it connects to the net via a modem. You are connecting the Mac Pro to the modem according to your text No the Mac is connecting to the router which in turn is connected to the modem- it's not seeing the network, but it is getting internet. Correct

Your use of airport seems to be that you are actually connecting to the netgear via wireless. Yes.

When you use ethernet to connect where are you plugging it in? Between the same Netgear router and the Mac. Does your netgear have rules set up? WEP and no blocks. Is that what you mean?

Could you try turning Airport off before connecting with ethernet and seeing if it works? The issue you may see is that you will have 2 leased IP"s from the router / modem.I loose everything if I do that.

Is the modem or the router the wireless source? Router.

Have you tired setting up a new user account?

System Preferences -> Accounts -> Plus button

If this doesn't work, try setting a new location in System Preferenes -> Network

Location is at the top, in the middle. Mine says Automatic at the moment.

Click on Automatic (or whatever yours says) and choose 'Edit Locations'

Again, hit the plus sign, call it testing 21-02-08 or similar and see how that goes.

Good Luck!

Touch wood the Mac is at the moment seeing the network computers. Seemed to help after I turned Airport on the Mac off then on. For the time being anyway.

The other computers are seeing but having trouble connecting. I'll work though that.

When the other network computers ask for a user name and password when trying to connect I assume it's the Mac's. One computer accepts it and connects the other rejects.

I'll post back how it goes. Thanks everyone.

Is that with a new user account or something else?

Same account. Did nothing else except turn the Airport off then on.

I don't think the problem is fixed but I can't reproduce it at the moment.

At least I've got a few other things to try if it acts up again.

Just thought I'd update on how things were going with the wireless networking problems I've been having. People responded with suggestions so it's the least I can do.

Most of the problems I was having seem better now apart from a couple I'm still working on.

When the Mac is switched on although the other computers on the network can see and connect to the Mac ( so the wireless is working ok) Finder seem reluctant to display the network. (blank Window. Sometimes the other network computer will show in Finder but only after some time. If not turning the Mac's airport card off then on brings it up.

Secondly on the networked computer the public folder is intermittent being able to connect to the Mac. The Mac hard drive and home folder has no such problems. This problem I thinking may be on the network computer (windows) and not the Mac. I'll look into that.

I was having problems also with the Mac not automatically discovering the network when first turned on. Even though wireless was turned on. In network preferences I unticked "Ask to join new networks" Problem fixed.

Thanks everyone for your help so far.