The professor I have selected to analyze in terms of the jinx is Gilderoy Lockhart. Lockhart, despite being a Ravenclaw, had set himself up for being taken down by being a terrible person to begin with. It was only a matter of time until his lies were exposed, so he went into the school year having a ton of baggage that the jinx would exploit at some point. The moment it all came crashing down, of course, was when he bragged about being able to take down the monster all on his own. His own big mouth got him in trouble, and he was put in a position where he had to show up, or be exposed. He tried to run and was, of course, found by Harry and Ron, and the rest is history.

As for the rest of the school being under some sort of curse, I don't think that is true. Due to the nature of our world, and the fact that magic is such a large part of our lives, dark magic is bound to be part of it as well. While it is unfortunate that so many terrible things happen at Hogwarts, a lot of it is usually unrelated, and there doesn't seem to be any evidence that all of it is related.