Error when processing dimension

When I process the dimension I get following error

Initiating transaction in Database 'CACI Cubes'
Processing Dimension 'BAL Periods' failed. No changes have been made to the
database.

Start time: 9:42:42 AM
Initializing Dimension 'BAL Periods'
Data source provider error: Login failed for user '(null)'. Reason: Not
associated with a trusted SQL Server connection.;42000; Time:3/23/2006
9:42:42 AM

Data source provider error: Login failed for user '(null)'. Reason: Not
associated with a trusted SQL Server connection.;42000; Time:3/23/2006
9:42:42 AM

Rolling back transaction in Database 'CACI Cubes'
Login failed for user '(null)'. Reason: Not associated with a trusted SQL
Server connection.;42000; Time:3/23/2006 9:42:42 AM



User is able to login to the db via enterprise manager and is a dbo. also
the data source connection test succeeds. I am not sure what could be causing
this error? any idea?