Windows

Point value changed by question poster.

Try this.

Go into the network card properties and Click the Authentication Tab. Uncheck "Enable IEEE 802.1x

This sounds like a wild problem I have seen before. It's worth a shot :)

Technet article 302088 says:


Wireless Network Adapters May Lose Connectivity When They Appear to Be Functioning
The information in this article applies to:
Microsoft Windows XP Home Edition
Microsoft Windows XP Professional
Microsoft Windows XP 64-Bit Edition

This article was previously published under Q302088
SYMPTOMS
A wireless network adapter may lose its IP address and, as a result, may not have any network connectivity to access the Internet or browse the network.
CAUSE
This issue can occur if the Service Set Identifier (SSID) for that network has not been added to the list of preferred networks. This can occur if infrastructure networks are detected and wireless detection has been set to auto configuration (the network has not been previously associated with and has not failed an 802.1x authentication attempt).
RESOLUTION
To resolve this issue, add the Service Set Identifier (SSID) of the network that you want to use from the Visible Networks list to the Preferred Networks list:
In the Network Connections folder, right-click the icon for the wireless connection that you want to use, and then click Properties.
Click the Wireless Networks tab, and then click Configure.
In the Network Name (SSID) box, type the SSID that you want to add, and then click OK.
If the SSID is not known or not yet detected, you may experience reception problems. When an SSID is detected, a message announces the SSID in the notification area, where you can choose the SSID for use.

You can also:

Right click the Network Interface Card (NIC), chose View available Wireless Networks, then click Connect. It is automatically added as a prefered network.

See if there's information here:

How to Troubleshoot Wireless Network Connections in Windows XP 313242

http://tinyurl.com/5qkc

Enable Windows XP Automatic Wireless Network Configuration 314897

http://tinyurl.com/5qkv

I have heard of several situations where xp has had some problems networking with 2000. in my personal experience, i had the problem too, and it was very beneficial to just upgrade the 2000 users to xp. if that doesn't work, then you should look at getting different network cables/cards for your computers. Sometimes you might have a damaged cable. also, you might want to look to see if there are any special drivers that you can use to help your network card function better.