Encountered the same(?) problem twice yesterday with 1.19i. In the first case I had made 3 out of my 4 attacks on a monster (wolf?), and when I tried to perform the fourth one the game refused to act. Similarly, I couldn't move the character. As opposed to Lord Cobol I hit End Turn instead. As my fourth blow should have killed the monster I suffered a few HP damage through its attack before my counterattack killed it.

In the second instance I was still advancing on the monster(s) when I suddenly couldn't move my troops. I could select the different troops, but couldn't move. Auto resolve, reload the save, and retry the battle worked successfully.

In neither of the cases were any spells involved (none cast, the monsters didn't have any abilities, and I didn't have any spell effects on my troops. I believe the tool tips still worked normally.