I'm afraid you have me stumped. I don't remember this bit. In "Underworld" there is a jump pad that is only enabled after you carry out certain other tasks but I don't think that's what you mean. I don't remember any "hard" jumps except for optional goodies. If you're still stuck, tell me which chapter you're in? It might jog my memory.
OT. Yes. I did have a hand in the site you found. My name on most gaming sites is "Greybeard". It was taken when I came here. "Greybeard" comes from the poem "The Rime of the Ancient Mariner". So ...