Here is another one for the Worst UI Ever series. This is from an application for a a very big software company's time tracking application. These kinds of things are part of the reason I developed Klok. You get this message when you select a project for your timesheet, but don't enter all any timefor that line item. To me, this doesn't even seem like an error. The system can easily ignore line items that have no hours.
At first glance, the message has to be one of the most confusing I have ever read. Click to enlarge it.
"You have entered time information without associating any time with that information. Enter time for this information, or remove it"...ummm....huh?
If you read it a couple of times, it makes sense. But you have to make an assumption about what "information" means. The user shouldn't have to assume or guess anything. If that this is an error that the system can't handle, would it have been impossible to say "You have not entered any time for Project X. Enter your hours or remove Project X from your timesheet". They even could have made "remove Project X" a link making it simpler for the user.
I find these types of issues all over the place. Usually they are due to laziness of the designers/developers or lack of commitment to the end user by companies in general. To a product owner this might not seem like a big deal. However, imagine a user getting this error the first time they use your software. What kind of first impression is that?
The number one thing to remember is that software is supposed to help people do what they need to do. It isn't meant to help computers do what they need to do.