This might be something funky with my own computer, but I sent one of my programs to a friend and he had the same problem.
Whenever I poll for an event as written in the code below, my program will close if I circle my mouse cursor around the top or bottom left corners of the window.
The problem is illustrated in this video: http://youtu.be/PD7-y1_H6qo?t=15s
You can try it yourself by downloading my pong game here: http://www.mediafire.com/?6xrvvtbr7qc03jo, but the same problem occurs in any program I make using the method below.
while(tetris.isOpen())
{
sf::Event event;
while(tetris.pollEvent(event))
{
if (event.key.code == sf::Keyboard::Escape)
tetris.close();
}
}