I have added a note with about 50 lines of text to an UML diagram in Visio 2010, and I can't resize the shape. I can see connection points, but not the blue ones that you can drag to resize the shape. Modifying the height manually through View menu, Task Panes, Size & Position, doesn't work either.
A note usually can only be resize to the minimum size of the letters inside. I mean that you resize the size of caracters or the shape of the note in order to get the smaller rectangle or square and the note should automatically resize themselves. If not this is a bug !!