It was my first job out of college, working tech support/help desk. I explained that I had career services help me with my resume, and that in the hurry to get the resume submitted I had not fully proofread it. He knew that I had applied and gotten an interview without having a resume submitted and that it needed to be in HR's hands before the first minute of the interview.

He was actually a pretty cool boss. I have to imagine that making that same mistake wouldn't fly in most places, which is why I mentioned it as a warning.