I once had a user call about a problem with a software package used in our organisation. Our desktop backgrounds contain the PC name and IP address in the top right hand corner. So I asked the user for her PC name so I can remote in and take a look.

I made the mistake of referring to the desktop background as the 'wallpaper'. She said 'Ok let me check.' After waiting on the line for about 2 mins, she came back on the phone.

'Sorry, we don't have any wallpaper, our walls are painted white'

I was speechless for around a minute.