Question : IAS authentication

We have a Windows 2003 IAS server for wireless authentication and it has worked fine for several years authenticating against the domain in which it is a member. We have set up new SSID's for various access needs in our network and another domain in the forest is being allowed to use the wireless network. Users in the other domain are not authenticated, the following error:
Access request for user domain\username was discarded.
Fully-Qualified-User-Name = domain\username
NAS-IP-Address = xxx.xxx.xxx.xxx
NAS-Identifier = WLC
Called-Station-Identifier = 00-13-19-36-dc-00:SSID
Calling-Station-Identifier = 00-22-69-2a-7a-eb
Client-Friendly-Name = WLC
Client-IP-Address = xxx.xxx.xxx.xxx
NAS-Port-Type = Wireless - IEEE 802.11
NAS-Port = 29
Proxy-Policy-Name = Use Windows authentication for all users
Authentication-Provider = Windows
Authentication-Server = <undetermined>
Reason-Code = 5
Reason = The user account domain cannot be accessed.

I tried to change the IAS serivce account to one that is allowed to query both domains for usernames and authentication but received the following error:
‘The account specified for this service is different from the account specified for other services running in the same process.’
How do I get the service account changed in all the places it needs to be changed, as I don't know what other services are running in the same process?
Any help would be greatly appreciated.
Thanks
David

Answer : IAS authentication

Added a few variablles below:

Usable?

Chris

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:



DECLARE  Team1_Nam, Team1_Res, Team2_Nam, Team2 _Res, Team1_Status, Team2_Status, Both_WPS
WIN = 3
DRAW = 1
LOSE = 0
WIN _WPS= 2
LOSE_WPS = 1
DISPLAY “Please enter the name of the first team.”
GET Team1_Nam 
DISPLAY “Please enter the result for the first team.”
GET Team1_Res
DISPLAY “Please enter the name of the second team.”
GET Team2_Nam
DISPLAY “Please enter the result for the second team.”
GET Team2 _Res 
IF Team1_Res = Team2_Res then
    if WPS then
ELSE
    DISPLAY “Was  the match won through penalty shoot out?”
    GET WPS
    if WPS = true
        IF Team1_Res > Team2_Res then
            team1_Status = WIN _WPS
            team2_status = Lose_WPS
        Else
            team1_Status = Lose_WPS
            team2_status = Win_WPS
        end if
    else
        IF Team1_Res > Team2_Res then
            team1_Status = Win
            team2_status = Lose
        Else
            team1_Status = Lose
            team2_status = Win
        end if
    end if
end if
DISPLAY “For this match: + Team1_Nam + Team1_Status ”:” + Team2_Nam + Team2 _Status