After SP2 I was unable to connect to SQL Server 2008. I found that the SQL Server Browser service was stopped. I enabled Browser, but it did not help. Everything was fine before SP2. My OS is Windows 7 64-bit.
Protocols for SQL Server: Enabled Shared memory, Named pipes and TCP/IP
Under TCP/IP, all settings seem OK.
A connection fails from the local network to this computer, but otherwise the server is working OK.