PEAP via Microsoft IAS does not work (using VeriSign Certificate)

Hi All,

I'd purchased VeriSign Certificate and installed it on a Microsoft Windows
2000 server with SP4 and latest patches. The server has been joined to the
Microsoft Windows 2003 active directory (2003 native mode). After
successfully installing the certificate, I reconfigured the Remote Access
Policy Rule (i.e. reconfigure the PEAP Certificate Issued to use the newly
installed certificate). Then we used the Windows XP Prof. Client (NON-domain
PC) to try authenticating via the Microsoft IAS service but we got the
following error.
"Access request for user <XXXXXX> was discarded.
Fully-Qualified-User-Name = <undetermined>
NAS-IP-Address = XXX.XXX.XXX.XXX
NAS-Identifier = Aruba-WLAN
NAS-Port-Type = 19
NAS-Port = 1
Reason-Code = 96
Reason = The authentication request was dropped because the session timed
out. "

Any comment are welcome.

TIA.

M C