Could you please check in SQL 2005 if there is enabled "Named pipes". (SQL servr configuration manager -> SQL server network configuration-> Named pipes -> enabled)
Are you using right credentials?
However I can connect to the SQL DB using a system DSN built in Windows. What is DSN? What are you using when you are connection to database. Is possible to connect by SQL managment studio from not machine, where is DB located?
If not work please create support ticket please.
Thanks for the reply. After much trial and error, I eventually got it to connect using this syntax: sqlservername\instance,port