What Is Different?

• What is different that could have provoked the problem or triggered the event? Was something new added or changed? Have any new applications been deployed? If changes have been made recently, consider backing them out and seeing what happens — does the problem still occur?

• Was the feature or functionality working correctly at one time? If so, what changed or happened between then and now?

• Is this working on another system? If so, what is different about that environment?