I've suffered several cases of clients that think "They Know Better" and wouldn't pay any attention to any explanation I could provide, and they would also fight every method I suggested to fix the issue*. Like it or not, there's people out there who don't want to learn.
And let's not forget the ones that are too stupid to learn any user-level IT. I've suffered a few of those as well.
Note *:This makes me wonder why the eff these customers don't just fix the issue themselves instead of wasting their money hiring an IT guy.**
Note **: Anecdotally, I've seen often customers in these categories trying to fix their computers by themselves, with predictably comical results.