Multi-line input controls have a few problems:
If their text becomes more lines than are visible, a scroll bar does not appear to look through them, you have to drag through the text with your mouse.
Dragging through the text with the mouse causes some minor problems, as seen on the left in the included screen shot. This was done by dragging to the bottom, and then back to the top.
If you highlight and delete the first few lines of text, and then undo the deletion, the text overlaps even worse, as seen on the right of the screen shot.
http://www.angelfire.com/hero/straygames/ByondBugs/ MultiLineInputOverlaps.png
The full text is "This is a test of long text in a box"