Database 11gR2, APEX 4.2.0, Apex Listener 1.1.4 running on Glassfish.
Within our APEX application (database user authentication), when logged in under user A (happens to be the schema owner), a button that runs a process works fine.
When logged in under user B, the error "1 error has occurred" appears. I believe this is the FLOW.SINGLE_VALIDATION_ERROR.
User B can see all the tables and the package (determined using SQL developer) within the process run by the button.