Why Linux Sucks

Once I was using thunderbird in some distro of linux, I can't remember. This was up to date, like a recent version of Kubuntu, just a few months ago.

Right I'm in thunderbird, its maximised, I go to close the window, I move my mouse hard up and right. I click my mouse, and what happens.... nothing.

See how the X button isn't at the exact edge of the screen, well I wasn't actually over the X button, so the window didn't close.