The Dink Network

I'm in the cave, found three of the artefacts, but where is the fourth?? I really want that light sword, because the fighting takes such a long time, and I am bored with it!
AND: I also went to see Albert Magnus, and he said something like "answer this correctly.." but then nothing happened! Only after a while, Dink dissappeared.
Are these problems bugs, or have I missed something?