SPOILER!
So I've been having the same ROT Final Battle blue circle/freeze also. I initially posted this over at Spellhold Studios, but I think this might be the more appropriate place.
I'm playing BG2EE, with the Sandrah mod. When I enter the battle area with Jaraxle & Entreri, both Entreri & Drizzt leave to the one on one battle area & Drizzt is removed as a party member. At the Drizzt & Entreri area, Sandrah & Pellegram are also present & my main character appears in the upper left of the screen & casts True Sight, even though I don't have that ability. The battle begins, Entreri appears to die, comes back, knocks Drizzt unconscious, Cattie-Brie shows up & shoots him with her bow, killing him. Sometimes his body remains, sometimes it doesn't.
Then dialog starts with Jaraxle, but the screen is still showing the screen where Cattie-Brie is. I click on one of my other party members & that takes me back to Jaraxle & Sandrah is there now too. I defeat Jaraxle, the shard is destroyed & then I'm taken back to the Cattie-Brie screen. My main character is present, along with Cattie-Brie & Entreri. Cattie-Brie kills Entreri & if Drizzt's body is present, it disappears & I get the blue circle & freeze. If Drizzt's body isn't there, then it just goes to a blue circle & freeze.
I sure hope there's a solution for this, I'm so close!