There is a cutscene conversation triggered as you approach the south east section of the cave. You talked to the old man who flagged the location on your map?
Try running the configuration program and switching to software mode (temporarily), and maybe reduce the resolution; that helps with some cut scene problems.
What point in the game are you? Have you been to the castle yet? Rescued Zandalor and let him teleport you somewhere? You can not over use the teleporter stones, but there are a couple places they get disabled (like the final room at the bottom of the catacombs).
