Adprep was unable to check the current user's group membership

[jaekim]

"Adprep was unable to check the current user's group membership"

I am trying to do
adprep -forestprep

so my windows 2000 dc and work with windows 2003.

but I am getting the following error.

does anybody know what to do?
=================================================================
Adprep was unable to check the current user's group membership.
[Status/Consequence]
Adprep has stopped without making changes.
[User Action]
Verify the current logged on user is a member of Domain Admins group, Enterprise
Admins group and Schema Admins group if /forestprep is specified, or is a membe
r of Domain Admins group if /domainprep is specified.

Adprep encountered a Win32 error.
Error code: 0x207c Error message: A required attribute is missing..

 

[Glenn L]

ADPREP must contact a global catalog and the schema master.
It appears ADPREP may be having problems contacting the GC.

I suggest you run netdiag and dcdiag on all your DCs to make sure all is
clean before proceeding with forestprep.