Comment 15 for bug 390446

I though I had the same problem, but after reading Slawomir's explanation I find that it's more a problem of the interface not behaving as the user expects, rather than the functionality being broken.

Indeed, when moving the window by dragging the frame it's not possible to redock it again (or I've been unable to do it). However, when I moving by dragging using the gray area just below, it's possible do it everytime without any problem.

Please see attached screenshot for a more descriptive explanation.