[Update May 2009] My collegue found a good tool online which could be very helpful for users to isolate issues related to this error message. You can download PortQry from http://support.microsoft.com/kb/832919, run "portqry.exe -n yourservername -p UDP -e 1434". If this command returns information and it contains your target instance, then you can rule out possiblity 4) and 5) above, meaning you do have a SQL Browser running and your firewall does not block SQL Browser UDP packet. In this case, you can check other issue, e.g. wrong connection string. [bold mine -mfn]

Labels: noteToSelf, SQL Server