We had serious headaches over this...
Make sure you have the client components installed;
Set security  permissions for the files - if just one file is not permitted
it will screw up;
Set your client machines to use the browser network password  at logon;
Make sure you are coordinator level.

Providing you are within the domain  or have a trust relationship with the
server from one domain to the other you should be OK.

We also used API token generation/ impersonation protocols and this will
work too although you still have to set the browser to allow authentication
through the windows logon  (see the security settings  in explorer).

if the above is no use - give me more details - we have set up two
independent transparent logons from windows to SPS and from a web site to
SPS.

but this did not solve  the prob.

>>Make sure you have the client components installed

installed

>>Set security  permissions for the files - if just one file is not permitted
it will screw up

I have removed the files just to make sure but still the error occurs.
Before each and every file was permitted

>> Set your client machines to use the browser network password  at logon;

How do i do this?

>>Make sure you are coordinator level.

I have coordinator permissions on the server (local account) and i am also
coordinator with my domain  account.

>>Providing you are within the domain or have a trust relationship with the
server from one domain to the other you should be OK.

yeah we have that.



Still the error occurs. I don´t get it. The error did not exist before I
migrated the folders and docs to the doc library. The files are taken from
the "old" sps-server. The error only occurs when i want to add a user to the
workflow or to the security setup. All other funtionalities like managent
etc. are working.

I very much appreciate your help...any help.

sorry only just spotted this...
go into the browser tools/internet options
then find the security  tab. Go to the internet options bit and then into
custom level.
now scroll down to the very bottom and then set the radio button for
authentication 'auto logon  with current username and password'. Assuming you
have a logon token you can pass seamlessly through into sps.
you can also use the logonuser API with this - just incase you don't want to
use the logon from windows.