I've found that people have a real hard time with anything that deviates from their normal daily activities. Give someone a new phone and all of a sudden they forget how to dial. Move a form to a different place on the network and now filling in a date becomes difficult. I don't know why this is, but I find it very confusing.
I don't think I've mentioned this before, but I work in the IT department for my company. So the two examples I mentioned earlier are from personal experience. I get to answer questions from my company's users on all kinds of computer, printer, and/or phone related topics. I found a website that is full of funny and confusing stories and I often check it out when I need a good laugh.
So whenever you think you deal with some really dumb people, go check that site out and laugh at someone else's misfortune. It always makes me feel better.