My coworker can connect to sql server using sa password. However, I can not do it. I get an error (Provider: Named Pipes Provider: error :40 - could not open a connection to sql server)(Microsoft Error: Error :53)
Do you have TCP/IP enabled for the native client? If you look under Start, Programs, SQL Server 2008 R2, Configuration Tools, SQL Server Configuration Manager you can adjust the protocols for the native client. I would imagine that you have TCP/IP disabled and Named Pipes enabled. Enable TCP/IP and then try the connection again. Hope that helps.