In Pool OF Radiance my cleric is completely out of my control and now behaves like an NPC.

I have no idea when it started because I was convinced I had just accidentally clicked on the Quick option in combat for awhile. She will now refuse to trade with anyone in the party, so if I give her an item to carry she won't part with it, and she will not pay for services for the whole party most times (boat transport, lodging, etc.)

She is totally out of my control during combat and is often a liability now.

I can control what spells she memorizes and make her cast healing spells on other party members when we are not in combat.

I also noticed that when we were in the Lizard Man Keep in the anti-Magic zone, she was casting spells!

I don't have a save game back far enough to fix this, apparently.

I am VERY far into the game and it would be painful to start again or level up a new character. Everyone is 6th level or over and the only missions left are the graveyard, and infiltrating Stojanow Gate. I was planning on taking these characters all the way through all four games. :(

I tried to get Gold Box Companion working to fix this, but I can't get it to find DOSBox no matter what I do, so the game just starts normally without any features.

Any advice would be great. Thanks!

It sounds like "quick combat" mode. Try hitting spacebar while one of the characters is moving on the screen:

https://www.gog.com/forum/forgotten_realms_collection/pools_of_radiance_turn_off_quick_combat_mode

It's not Quick Combat mode. I hoped that's all it was so I could turn it off, but it's not just combat. She won't trade with anyone in the group, and she won't pay for party expenses, and when she is in combat she also casts spells even in the anti-magic area of the Lizard Man keep when no one else can.

I can't use the character editing functions of Gold Box Companion since it craps out and says it can't find DOSBOX whatever I do, but when I looked into my save games in the Windows element of Gold Box Companion I could SEE all my characters and all their levels were listed EXCEPT the cleric that is going crazy. She just has a blank area where her level should be listed.

Thanks for the offer, that was awesome of you.

I just gave up and finished the game the way it was. I replaced that bugged character when I exported to Curse of The Azure Bonds when she wouldn't export, but my party is better balanced now anyway.
Happy adventuring!