One of my early sins involved moving a local newspaper group's archive from a room filled with boxes and boxes of physical newspaper clippings to a web based digitzed library - and the journalists having to switch from shouting at the library staff to find them something to jumping on a shared PC and searching for things themselves.
Now most of these people were reasonably intelligent and had been using 'computers' for years...but those were dedicated publishing terminals with crazy keyboards covered in buttons to do anything and everything, not IBM PCs with their simple keyboards and new-fangled mice. Things started well, with most of the staff picking it up quickly and not reporting any issues, and then I get the call...
Them: "The mouse isn't working properly"
Me: "What's happening?"
Them: "I do my search but when I click on the link with the mouse thing sometimes it works, but usually it doesn't, and sometimes it opens a different link"
Now you don't have to support users for very long before you know that 90% of "That just doesn't make sense" issues aren't in either the hardware of software but in the pinkware. One quick trip downstairs and a "Can you show me the issue?" and I see them at work...
1. Gingerly move mouse, holding it between the tips of thumb and first finger, like you think it's a ive hand grenade till it's over the link.
2. Withdraw hand from mouse.
3. Index finger out.
4. Hammer down on the left mouse button from a height of 2ft, possibly with eyes closed.
Yes it did click the mouse button. It also tended to move it a random distance in a random direction on the desk and so the pointer on the screen.