When training a unit from the city build dialogue the 'Train' button to order the unit is just above the 'Train' button to open the dialogue. I tend to press the lower button assuming I've ordered a unit instead of the button just above it. If this dialogue opened in the centre of the screen it wouldn't be an issue or if the name was changed it may also help.
This issue isn't such a big problem for the 'Build' button because you tend to place buildings on the map.
