My current code is using al_get_mouse_state and al_get_keyboard_state (I'm not using events for input.)

I'm getting a consistent 60fps with vsync turned on.

Mouse movement is smooth until I hold down any key. Then it becomes very jerky and laggy. I'm writing a little map editor and alt+drag scrolls the map. I tested with and without requiring the alt key and verified the problem I described while holding any key.

It's very strange because I don't think I've ever seen this before in previous programs. Could be an Windows thing maybe. I'm testing with a touchpad on a laptop.

Anyone encountered this before?