I'm having a problem with HL (I know it's hard to believe but I'm playing it for the first time ever). I've been going through the Black Mesa training, and have gotten to the part where you get on the train and hit the use key to travel forward into a dark tunnel. The lady's voice says I've passed my training course, but the screen goes black , I can't move, and the game goes back to the main start menu screen. What gives? WTH am I doing wrong?