Can't start Mirror

Dear Sir,
I have 3 Server for testing Mirror.
my first server is :192.168.1.10 and name is : MIAMIDC (Principle, Window 2003 Enterprise and has promote to Domain Controler(ACLPCA.com))
my second server is :192.168.1.20 and name is : MIAMI1 (Mirror , Window 2003 Enterprise and joint with MIAMDOC(ACLPCA.com)
my third server is :192.168.1.30 and name is : MIAMI2 (Witness , Window 2003 Enterprise and joint with MIAMDOC(ACLPCA.com))
When I run : alter database [Adventureworks] set partner='TCP://192.168.1.20:5022' on 192.168.1.10 it show the message error :
The server network address "TCP://192.168.1.20:5022" can not be reached or does not exist. Check the network address name and that the ports for the local and remote endpoint are operational.
Can you help me to solve this problem ?
Thanks

Hi,
I've faced same problem while i set up mirroring. What I made a mistake is i've restored the database with recovery and then i tried to configure database mirroring. Then I dropped the endpoints from both principal, mirror and witness and restore the database with norecovery option in mirror and then configured mirroring..
Regards,
Mani