I noticed an issue where the current line highlighting feature will sometimes highlight the wrong line. You can reproduce this in the SDI Editor sample application. Turn line highlighting on and select a line. Turn line highlighting off. Move the caret to a new line by clicking or by keyboard. Turn line highlighting back on. You'll notice the line that is highlighted is not the line that the caret is on. As a side note, if you turn line highlighting on before clicking on any line in the document, no line is highlighted until the caret is moved.