This is happening to me as well (extremely rarely though). It happens on competitive gameplay, once multiply directional keys are being pressed (wasd). I might have to restart the game to resolve it. I have connected the keyboard on both onboard usb 1 and on nec usb 2 pci card. Perhaps it's due to keyboard itself (being cheap and not gaming with anti-ghosting capacbilities) or perhaps it's the Q3 port.