I was getting the following error when trying to browse to the K2 Workspace page:

Server was unable to process request. --> Login failed for user '(null)'. Reason: Not associated with a trusted SQL Server connection.

The K2 databases were on a separate server and K2.net Server was running on a different server.

This issue was resolved with timely help from the K2 Support Team and involved changing the Web.config file located at Program FilesK2.net 2003K2WSWorkspaceService to use SQL Authentication in the database connection string as follows:
<add key="DSN" value="Data Source=SQLServerName; initial catalog=K2Log; User ID=username;Password=password" />
instead of Windows Authentication:
<add key="DSN" value="Data Source=SQLServerName; initial catalog=K2Log; Integrated Security=SSPI" />


Thanks....