There have been a couple of issues that keep pestering the SQL Server community for those that use Vista as their client.
Example: SQL Protocols Blog entry
Now Microsoft has created a KB on it: http://support.microsoft.com/kb/936302,
I have tried and tested a solution that fixes this, and it is related to the KB, that was not available for some reason when I originally had the problem. So the steps that I took to solve it are as follows:
- Open Windows Firewall in Control Panel
- Go to the Exceptions Tab
- Click on Add Program
- Find SQL Server Management Studio and click OK
- Test the connection
I did this several times with enabling and disabling the firewall and having consistent results that I could now connect to the Windows 2008 Cluster that had SQL 2005 Failover Instances on it. I then went to a colleagues workstation and it fixed it as well.