I have been fighting this one for days: my computer is currently joined to our corporate domain, but I am logged in as a local user. I've used "Manage network passwords" to add all of the relevant credentials for domain access. However, I still get the following error when logging in via Windows Authentication in SSMS:
Login failed for user ''. The user is not associated with a trusted SQL Server connection.
The error logs show that the SSPI handshake is failing - meaning that Windows is not passing along my valid domain credentials to SQL Server.
Finally, I found a workaround that deals with what I'm experiencing by making use of the runas command. It's hacky, and this is definitely due to Vista's "wonderful feature", but it gets the job done. Thanks to Jason Follas for the following tip:
For the record, we should not have to do this.