Remote dtc security problem

I have 2 computers, one as server (server 2003) and other client (vista
business). both are in same domain. Application consists of server part (IIS
on server 2003) and client part (winforms on vista). client is configured to
use remote dtc on server. when client starts opening distributed transaction
i get message
"MSDTC was unable to read its configuration information. (Exception from
HRESULT: 0x8004D027)"
But when I add my domain user (under which is winforms client running) to
server Administrators group, distributed transaction works fine.
I believe there is something with security...