Friends, in the last hour or so I have had the following happen:
1) In the slaveholders stronghold, after killing off the Troll, I can't get into the last room (as I restarted the game a couple of days ago, I remember there is a young child there, but I can't get in to see him anymore).

2) Although I have met with Melia (?, the lady with the castle) and my map is marked with the castle; with Umar Hills; and with the Mountains (?name), I can't go to any of them.

3) Although this may be normal, Jaheira got turned into stone, and disapeared from my list of characters (she's a great statue somewhere behind the Coronet, and maybe this is a blessing).

Any ideas?

Did you pick up the slaver's key? It should be on one of the bodies, near where you fought the troll. You cannot move to areas outside the city until you first move to the city gates. Try a stone to flesh spell on Jaheira.

The trolls thing in the sewers happened to me too- kinda a bug- but avoidable. Basically the trolls are so big that one of two things has happened if I wasn't careful- one is I opened the door on a troll one time and I guess I caught his foot or something- he was stuck there couldn't get in the room or even see him to kill him- had to reload- thank goodness for auto saves! The other thing that happened is I stood there in the doorway and killed all the large fumbling idiots and the pile of bodies was so large I couldn't walk through the door! Again- reloading. I found the best way to avoid the problem is to line everyone up ready to attack way back by the boxes in the center of the first room- have your thief go open the door- kinda say na-na-na-boo-boo to the trolls to get them coming after you and run back out and fight them in the other room well away from the door.

As for not being able to go to these places- did you go to the city gate and walk through the gate to get there? Makes a difference. As for turned to stone on Jaheria- I would just thank whoever didit myself- but if she's still in your party then just go to the temple- or reload.

Thanks, Wesley, Tara. Great advice! I think I'll let Jaheira be ornamental for a while - so much complaining!

Give her a break. She stops complaining relatively quickly, and she gets excellent druid spells.
Again, I can't stress how useful insect plague is.