ToME: the Tales of Maj'Eyal

The leveling up system allows you to take out points from a skill that you do not have the prerequisites for, (because for example you leveled it up earlier, and then took off the equipment which gave you the necessary boosts to level it up), but then will not allow you to leave the skill screen, giving the message: Cannot level skill so and so, does not meet required prerequisites. Furthermore, you cannot put the skill point back into it, because you do not have the required stat. So the game is stuck at that point.

So for example, I had put 5 points into unflinching resolve as a brawler, but must have switched my equipment at some point, because I no longer had the required con for that level. I took a point out of it to put into something else, and then was stuck permanently in that screen, because I could not put the point back in, not having the required stats. This sounds a little convoluted, but it's easy to reproduce.

Hum but can't you just escape by cancelling?

No, when you try to escape it says it is not allowed because of the talent that you downleveled and cannot level back up. Prereq not met. I'm sure I tried that, because I tried everything before resorting to killing the process and reloading.

Edit: NVM, just tested it again - you cannot cancel it, but if you hit escape and say you do not accept changes, it brings you out. I guess I was just trying to hit cancel when the message popped up asking whether I accepted changes.