Vague error in log "You do not have permission to access this page."
Try this extension

https://civicrm.org/extensions/civicrm-error-handler


  Sometimes CiviCRM can be real tough to debug. Especially when you are getting fatal errors, but only by some users, and you can't recreate the problems. This utility will send you a detailed email when a CiviCRM fatal error occurs.