I think users almost always tend to blame themselves for bad UI because it makes them feel stupid. Therefore I think they tend not to complain.

When users raise an issue like this, I try to show empathy right away. I know they are already on edge thinking: "Am I the stupid one?" Of course, there are users with nothing but packing peanuts in their brains, but the good users with real brains... be good to them when they raise an issue!

Same. My default position is that the UI is wrong, not the customer. Obviously not always true, but for me, a good working assumption.

I agree. The knee jerk reaction of many otherwise highly educated corporate users when there is a UI issue: "Oh, I must be doing something wrong." So often, something is wrong on the server that is causing horrible lag or weird errors.

It is more amazing when you meet a very resilient user (think: senior sales staff -- they'll do /anything/ for a sales commission!). They just assume this is normal operating procedure. Only when things are horrible, do they ask for help. Then, you stand behind their desk and watch in horror at all the bugs they workaround (many times per hour!) in your app, but never report... Hat tip to these amazing users!