SQLISPackage100 Error on Cube Processing via BPMC Scheduler

An error can occur in SQL Server 2008/SSIS environments where the feeds run fine in the Load Data panel of the data process control, however, will fail when scheduled using the BPMC scheduler.

The error message in the Data Process Control says the following:
"Job failed on Analysis Services processing. Click on Jobid for more detail"

When the jobid is clicked in the DPC, the following details are presented:
"There was a problem with cube processing. Please reference SQLISPackage100 errors on the SQL server application event log more detail"

The occumpaning error message in the application event log reads the following:
Event Name: OnError
Message: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> Microsoft.AnalysisServices.OperationException: Either the user, NT AUTHORITY\NETWORK SERVICE, does not have access to the database, or the database does not exist.

This error is caused due to the way xp_cmdshell in SQL Server authenticates to Analysis Services.

To solve this problem, run the following command in SQL Server:
xp_cmdshell 'whoami.exe'

This command will tell you what account xp_cmdshell is running under. Once this account is identified, explicitly add it to the analysis services security policy. This will allow xp_cmdshell to process the cubes with the correct privledges.