Did you check right afterwards if you were able to hit the enemy by normal means with a melee weapon?
There is one issue with melee fighting in general: The melee range is very limited, it's less then 1 tile actually but no two characters can stand on a same tile. This has the consequence that a NPC (or the player) can stands between two or more tiles when the turn based mode was initiated while he was moving or when he didn't have enough MP to complete his movement to the desired tile. If there are enough "free" tiles around him your character will move to the tile he can attack from and strike, but if there is only one tile next to the enemy and he's blocking it partially you won't be able to hit him with melee, or in your case with Cut-Throat which is melee range.
Edit: This can be tested easily with any melee enemy and a door, for example rathounds in the underground outposts with the fence doors. Spend all your MP with only 1 or 2 left and move to the last tile between you and the enemy. He won't be able to hit you because you're "barely" standing on a tile he would have to walk on but he can't because it counts as occupied. Like I said, the same applies to the enemy placing so I bet this happened to you. In my last melee game I had this situation only maybe 3 or 4 times but it does happen. The solution would be to increase the melee range just below 1 tile so you can't hit enemies across 1 whole tile but can hit those that partially stand on it.
Edit 2: lol Niven I didn't even notice that you resurrected a 1 1/2 years old thread. Why would you do that in an unfinished fast changing game? Still, the issue I described is yet present.
