Adding users from multiple domains to a local group

Environment: Web application adds users from multiple domains to a local 
group. The code that does this uses ADSI (WinNT provider) and runs in a
COM+ 
component using the identity of an account that is part of the local 
administrator group. Server is windows 2003. 

Issue:
   Set objAdsUser = GetObject("WinNT://" & sDomain & "/" & sUser)
   is returning -2147024843 (path not found).

The code that searches for the users before attemption the add is working 
properly and returning the list of users. It uses the LDAP provider. 

If I log in to the server using the same account as the one that the code 
runs under, I am able to select and add the users from that domain to a
local 
group using Computer Management. So it does not seem to be trust issues or

accessibility to the domain. Would anyone have an idea of what to look
for? 
Or perhaps how to code this feature, so that I won't run into this issue
and 
have it behave similar to Computer Management? 

Thanks