menu chooses to align to wrong boarder

[EDVdoG]

Noscript 2.6.8.19
Iceweasel/Firefox 28.0

I don't allow scripts. If I go to http://guess-that-key.blind.guru/ and allow both blocked sites, the next time I open the dropdown menu, the menu is not aligned with the noscript-icon but retains the former leftsided position. See for yourselve:
1. nothing unusual: http://imagebin.org/302330
2. allow both sites at once: http://imagebin.org/302331
3. go back to the website so the menu is closed.
4. next time I open the drop down menu it looks like: http://imagebin.org/302332
This behaviour is most obvious if the browser is in fullscreen but the dropdown menu will align to the position as seen in No1 in windowed mode, too.