I've noticed it's happened to me more frequently when I first select a team and the spectator camera places me "out of bounds" of the map. I'll see the skybox in the background and it'll just freeze up on me with the sound looping until I do a hard …
Edit: Played a full match as Marines without issue after installing Razer's Gamebooster and setting Infestation to minimal, textures to low, and turning off atmospherics. Mods can lock the thread.