One of the data sources available when using Cognos 8 is a SQL Server database. You may occasionally experience problems with your database connectivity from within Cognos Connection. This could produce errors such as “SQL Server cannot be found” or “Access Denied”.
If this issue occurs then you should start off by investigating if you configured named pipes instead of TCP/IP protocol as the default network library in the SQL Server Client Network Utility for a SQL Sever reporting or content store database.