Portal Trouble V.2

[Fuelbi]

Alright, so remember the thread I made while back about this game and the trouble I had making it to work? Well, yesterday, a bud fixed it for me. When I asked what he did to it, he just said that he did something with the right click button, but he didn't remember what he did after since he was just doing random ****. Anyways, all day yesterday the game worked and I finished the game and everything. Today in the morning it was also working. Now that I want to play again, it's gone back to its old ways and during the loading screen, it gets cut off and the screen goes black. I know now that the black screen isn't supposed to happen because it stays for much more longer.

I want to know why it suddenly stopped working again after beating the whole thing yesterday and starting the bonus maps today.