Client Problems

Everytime if I want to close the window of a transaction in the store the only thing that happens is that the X on the right top corner vanishes and thats it. So I can't close the window anymore and I can't close anymore too, because the "Exit" button is placed behind the window of the transaction so i can't press "Exit" to close League. The only way to close League is via Task-Manager.

Please fix this quickly. Thanks