I suspect a firmware upgrade probably fixes that behaviour. If you want to accept both computer credentials and user credentials you'll need to name both "Domain Comptuers" and "Domain Users" in your policy.By default, XP will re-authenticate with the user credential after the user logs-on (there is no way to do computer-only with XP, I believe).
You can access the Repair capability through the Repair context menu option of a connection or from the Repair button on the Support tab of the Status dialog box of a connection.
When you repair a wireless connection, it is disabled and re-enabled, which clears many error conditions on wireless network adapters.
If the authentication fails and the association is still in place, the wireless adapter is enabled and TCP/IP performs its normal configuration process.
If a DHCP server is not found, it automatically configures an APIPA or alternate address.
For background information, see Wireless LAN Technologies and Microsoft Windows.
For detailed information about a Windows-based authentication infrastructure, see Wireless Deployment Technology and Component Overview.
If an authentication requires additional information from the user, such as selecting one of multiple user certificates, a text balloon appears instructing the user.
Within the Network Connections folder, the text under the name of the connection corresponding to the wireless network adapter indicates the status of the connection.
WPA2 is supported as i can connect to WPA2 personal APs. During the connection it flashes that it "connected" for a second then goes to "Validating Identity" which it eventually timesout on.
I am using the Windows Wireless Connection Manager. On a couple of occasions I've seen that particular AP (don't know what firmware) suddenly stop attempting to authnenticate clients (it never sends any RADIUS requests) and power-cycling the AP "fixes" the issue.
Figure 1 shows the information available for a wireless connection in the Windows XP Network Connections folder.