I had a similar issue with SQL Server 2005, please try the suggestion below.
Check Programs|SQL Server 2005|Configuration tools|SQL Server Surface Area Configuration.
In "Surface Area Configuration for Services and Connection", you click on the service and remote connections.
See that you have local and remote connections activated.
Chris Powell
George: You're kidding.
Elroy: Nope.
George: Then lie to me and say you're kidding.