Please tell me about a time when something major didn't go according to plan at work.

Responding to situations that don't go according to plan is a key characteristic that interviewers look for. They will ask you a question like this to determine how you react to unforeseen circumstances. This provides them an indication of your flexibility, responsiveness, and creativity.

"During a recent software update project, the versions of the software we ordered were not correct. We reviewed the purchase order and determined that the software had been ordered incorrectly. Since the software seals had been broken, we couldn't return the product, nor was the manufacturer likely to agree to correct this because it was our error. Even though this involved additional expense, my manager and I agreed it would be quicker to order the correct versions of the software so we could proceed with the upgrade. We did this and were able to install the software without any major delay in the project. This taught us to carefully review the software versions we had and needed before ordering new products or performing any upgrades."