I normally go about 8 or 9 patrols where the game runs fine (GWX), then I will get a patrol (particular when I get thrown out of high TC due to being attacked or spotting a ship) and the music starts its dreaded loop - next thing i'm looking at my desktop without a trace of SH3 being played for the last 5 hours!
I normally crack the sh*ts after the game does that to me and I wont play it for a couple days. Always end making up and moving on however