With the draggable circles - click, drag, move the mouse outside the rectangle, release the mouse button. Now move the mouse back inside the rectangle, and it still thinks your dragging, even though you’ve mouse-up’d.
I guess this is because it’s not catching the onmouseup when you’re outside it’s “domain”. Perhaps make it automatically trigger the mouseup when the pointer leaves the area?
dojo.gfx thing is cool - but what caught my eye in the above-linked article is the above-quoted comment. Drag and drop and missed mouseups seem to be an issue everywhere. I can't seem to get around them in my XoxoOutliner drag code, YUI DnD examples seem to suffer from it, and hell - even Firefox itself doesn't seem immune: Try drag-selecting some text, wander off-window with the mouse, release the mouse button. For me at least, on my Mac, the drag-selection keeps doing its thing when I wander back on-window. No me gusta.