IAS with Symantec 320 Security Gateway

I’m trying to configure IAS Radius to work with my Symantec 320 Security
Gateway. I have it working to the point where IAS responds with a username
and password prompt. The log on the Win2003 server logs that I've
authenticated but I get dropped right after that. The only errors I get are
in the Security Gateways log file included below.

Any help would be welcomed.

11/09/2004 05:22:05.82 Wan Client - STATE_TRANS_WAIT_I1 ISAKMP XAUTH done,
waiting for ISAKMP Config
11/09/2004 05:22:05.72 Wan Client - STATE_TRANS_XAUTH_R3 sent ISAKMP xauth
set status, expecting ack
11/09/2004 05:22:05.72 RADIUS ACCEPT (user=mattl)
11/09/2004 05:22:02.07 Wan Client - STATE_TRANS_XAUTH_I3 sent ISAKMP xauth
password request, expecting password
11/09/2004 05:21:59.67 Wan Client - STATE_TRANS_XAUTH_I2 received ISAKMP
Config, sent ISAKMP xauth username request, expecting username
11/09/2004 05:21:59.67 Wan Client - STATE_AGGR_R2 ISAKMP SA established
11/09/2004 05:21:59.52 Wan Client - STATE_AGGR_R1: from STATE_AGGR_R0; sent
AR1, expecting AI2
11/09/2004 05:21:59.17 Wan Client - Responding to Aggressive Mode from
Remote Peer 209.181.252.149
11/09/2004 05:21:58.57 Wan Client - Terminating connection
11/09/2004 05:21:58.57 Wan Client - Terminating connection
11/09/2004 05:21:58.57 Wan Client - Sending ISAKMP OAK INFO (Notification
IKE SA)
11/09/2004 05:21:58.57 Wan Client - state transition function for
STATE_INFO_PROTECTED failed: PAYLOAD_MALFORMED
11/09/2004 05:21:58.57 Wan Client - STATE_TRANS_WAIT_I1: PAYLOAD_MALFORMED

11/09/2004 05:21:58.57 Wan Client - ERR: malformed payload
11/09/2004 05:21:58.57 - ERR: byte 2 of ISAKMP Hash Payload must be zero