After e few minutes of playing Ultrastar deluxe, some songs can't be launch ("La chanson ne peut pas être chargée"), but if I restart Ultrastar, these songs work...but problem reappear after a couple of minutes... I tried with nightly build but problem persists. I tried too to copy ultrastar from another computer (and it works well on it...).
W7 x64 Ultimate
Nvidia GTS 250 drivers up to date
4 Gb RAM