I'm also having a problem getting rid of an NPC party member. He's always invisible and no-one can talk to him to say so long. He is untouchable in combat and out of it from both friendly and enemy fire so there's no hope he'll die. He just stays invisible and 'untouchable'. His name is Frederic Bertram and I got him in Nubil after beating Tobil in a boxing match. Now I can't get rid of him, he's like a bloody pirate ghost that follows the party around, somehow accumulating booty and taking experience points yet doing nothing to contribute in battle (well he can scout with impunity as the enemy always totally ignores him, but this feels like cheating to me). Not only is he always invisible and incommunicado but he take up no space ie another NPC or a PC can occupy the same space as him. Casting 'see invisible doesn't make him visible.
I'm starting to think its another 'bug' in the game.
The gameplay also leaves a lot to be desired like combat targeting and picking up loot afterwards. At one stage Cuthbert attacked (no idea why maybe they sometimes hate the Bertram-pirate-ghost) and so did all the people of Hommlet and several of those of Nubil until I reloaded from exiting TOEE then this time only Cuthbert attacked me but now I cant claim his booty as he fell next to the exit door, its so frustrating seeing fallen booty but not be able to snatch it!
I don't think I can do anything about Bertram-ghost unless I restart the game...unless maybe there is a way to hack the save game file and remove him?