(Some minor spoilers included as I need to give examples.)
I don't know if this has come up before but has anyone experienced problems with members of the party suddenly disappearing in combat? By this I mean that: (a) they disappear from sight; and (b) they are no longer in the party at all (their portrait vanishes). This is not due to the Impriosn spell either. I have had two occasions where a member of the party suddenly disappeared during combat, yet nothing in the combat messages suggested that anything unusual had happened to them.
First time was in Underdark, fighting some powerful wizard (he cast time stop and a couple of other high level spells, though could have been scrolls I guess). During the battle Viconia suddenly vanished. Ahhh. "Imprison" spell I thought. So, after the guy was dead I checked the battle output. No mention of Imprison. Hmmm. Got Nalia to cast a Freedom scroll just in case. Noticed that Viconia was visible again, though I am not sure if it was due to the spell or not, and in any case I couldn't talk to her. Neither was she in the party either. Somewhat miffed by this I used the Ctrl-Q cheat to force her back into the party, whereupon I discovered that she had zero hitpoints. I tried healing her... nothing. Tried resurrecting her... nothing. Checked her inventory screen... everything greyed out. Checked her stats screen... nothing unusual, not affected by any negative spells. Weird. (I should mention that I lost Korgan to an Imprison spell in this area too, yet he came back successfully after a Freedom scroll.)
Next time it happened was in Hell, fighting some Beholders. Jaheira suddenly disappeared during the fight. Since when did Beholders cast Imprison? Anyway, I again checked the messages, and again there was no mention of Imprison. One moment she was there, the next she had gone. I got Nalia to cast Freedom again (and yes, it was in the same area). Nothing happened. I walked around the area but she was nowhere to be seen. I went through the exit but she wasn't on the other side either.
Are these bugs or is there something I don't know about going on?
Disappearing party members (minor spoilers)
A good way to test if they are petrified is to smack them once with a sword. Makes a big chunky splat if they are. Of course this will remove them from the game permanently though 
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"Four thousand throats may be cut in one night, by a running man."
- Klingon Crewman "Day of the Dove"

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"Four thousand throats may be cut in one night, by a running man."
- Klingon Crewman "Day of the Dove"
"Four thousand throats may be cut in one night, by a running man."
- Klingon Crewman "Day of the Dove"
- Klingon Crewman "Day of the Dove"
Turned to stone... sheesh, never even thought of that. (I'm new to this, and I'm sticking to that excuse.) 
Will keep an eye out for it happening again and check. Vic was still "there", but I didn't notice Jaheira. However, since I wasn't looking for someone turned to stone I may have just missed her.
Thanks a lot for the tip

Will keep an eye out for it happening again and check. Vic was still "there", but I didn't notice Jaheira. However, since I wasn't looking for someone turned to stone I may have just missed her.
Thanks a lot for the tip

Disintegration spell also does that. Permanent NPC loss. 

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