Secure Wireless not working in VISTA

I am facing some problem when I try connecting to my wireless network with
CISCO ACS Certificate . To explain in detail, in my office network there is
wireless connection and I was able to connect to the same without any issues
when I was using WEP key .But last week they moved to this authentication
based on certificate (CISCO ACS) and then I am not able to connect from my
VISTA. We are using CISCO Aeronet 1200 Series(AIR-AP1231G-A-K9).Employees who
use XP are not having any issues. These are the steps that I did


In the properties, security tab and
In the security type drop down values I chose 802.1X and
In the Encryption type drop down WEP.

In the network authentication method drop down I chose PEAP and checked the
checkbox next to "cache user information for subsequent connections to this
network "then
clicked setting and in the window that opened

I have enabled "Validate Server certificate" and in the Trusted Root
certifcation Authorities I have enabled the certificate that was given by my
network team and which I installed in my PC.

I have enabled "Do not prompt user to authorise new servers or trusted
certification authorities".


In the "Select Authentication Method" drop down I chose EAP-MSCHAP v2 and I
have enabled the "Enable Fast Reconnect" option as well.

Then I clicked "Configure" button and have enabled "Automatically use my
Windows logon name and password (and domain if any)

DETAILED LOG:
--------------

Root cause:
Windows cannot connect to "mobile"
Windows was unable to verify the identity of the server.

Detailed root cause:
EAP authentication failed because Windows could not verify the authenticity
of the server's certificate
Workaround for hypothesis: Contact the network administrator for "mobile"

Information for connection being diagnosed
Interface GUID: {50e2e69e-29ab-47af-9401-e19158427ae4}
Interface name: Intel(R) PRO/Wireless 3945ABG Network Connection
Interface type: Native WiFi
Profile: mobile
SSID: mobile
SSID length: 6
Connection mode: Infra
Security enabled: Yes
Connection ID: 8
Security settings provided by hardware manufacturer (IHV): No
Profile matches network requirements: Yes
Pre-Association and association status: Success
Security and Authentication:
Configured security type: Open
Configured Encryption type: WEP
Security connect status: Fail 0x0003800b
Number of security packets received: 6
Number of security packets sent: 6
802.1X protocol: Yes
Authentication Identity: Invalid
IAS Server engaged: No
EAP Method supported by IAS Server: Unknown
EAP type: 0
EAP Error: Unknown
Number of 802.1X restarts: 1
Number of 802.1X failures: 1
802.1X status: Fail 0x00050005
Key exchange initiated: No
Unicast keys received: No
Multicast keys received: No


Event Verbosity:0