This issue may occur if the user who owned or created the process has their rights revoked.  This most often occurs when the user leaves the organization - rather than deleting the user record, many choose to simply remove that users' system roles so they can't access anything.  However, this means that any business processes or queries that they owned will no longer be able to pull in results.  

In version 3.0, we added the Business Process Ownership tab to application user records, which provides a list of all of the business processes owned by that user.  When a user is having their rights revoked, a system administrator should review the processes on this tab, and assign those that need to be kept to a new user.  This can be done by expanding the process, clicking "Edit owner" and selecting a new application user as the owner.

To identify which queries an application user owns (which may be impacted if we revoke that person's rights), take the following steps:

1.  Go to Analysis > Query > Add an ad-hoc query.  
2.  Choose a source view of "Ad-hoc query."
3.  Add a filter of "Owner is equal to [application user]
4.  View the results, and identify queries that will need to be used once the user leaves.  
5.  Open each of those queries as another user (ideally, a system admin) and re-save them - this will update the owner on the queries to the new user so that they will continue to run successfully.