[Acc 10.4.1, W8.1, HP Pavilion g6-2306el]
Steps to reproduce the bug (how it happened in my case, at least):
1. Open HMT-W4 and go to Ezek 44:30
2. Select the first half of the text (all the way to the 'atnah)
3. Click the 'Language' option in the toolbar, and select 'Diagram'
4. In the diagram window, drag a selection area, even reaching all the way to the extreme left, where the tool icons are.
5. BUG 1: Click outside of this selected area, and the rectangle is still visible (even on top of the tool icons).
6. BUG 2: Press Ctrl-Alt-T to detach the tab, and the program crashes.