Half-Life 2 issues

[lil' brudder]

I am running Half-Life 2 on my Core Duo 1.83 Ghz 2GB RAM Win XP Pro whitebook and the game has run great up until the part right before I would go up a certain set of stairs near the blue tower after I take out the three generators, when it loads the next part, it glitches and I end up stuck in midair outside the stair guardrails. If I save, the saved game has a black screen as the screenshot and if I even click the load saved game button on the main menu, it crashes. Any ideas? it makes me really mad that I was so close to finishing it and it was running relatively glitch free.... Any help would be much appreciated. Thankyou!