Writing to one Active directory from another Active directory

Hello All
I have a question that I am hoping someone can help me with. Where I work we
have five seperate domains and hence five active directories. All of the
domains are joined together by a second network card for backup purposes. As
we have five networks some users have five accounts and this becomes a
problem for passwords. I have set up trusts between all of the active
directories and I can look at the users and computers on one domain from
another but every time I try to change the password on the remote domain I
get an access is denied error. I have also tried to do this through VB
scripting and when the script writes the new password I get a runtime error
70. I get the feeling I am missing something small and even looking around it
may have something to do with DCOM but I am not an IT person by qualification
so I am not sure what I am looking for. I am looged in to all domains as
Administrator when trying this and our networks are server2003 sp 1. Thanks
for any help