A couple of problems I've encountered in Underdark:

1) After agreed to meeting with Solaufein in the south-east corner of the main tunnels to resque a drow from the Illithid I head over there but no Solaufein.
Is there something that must be done before he appears?

2) The Imprisoned Souls: When I'm fighting Raevilin Strathi Minsc suddenly disappears (no Icon, no nothing) and his stuff turns up in the other characters' inventories. There is no explanation to his disappearance in the dialog window.
Is this something that can be avoided?

Odds are Minsc has been imprisoned (freedom scroll from Duergar camp in south-west). I never noticed items going into your inventory before, but that mage casts impronment at you. Kill him quickly and prevent him from casting spells. I'm sure you have your own tactics for that stuff.

Solfn. is definitely in the south-east over the bridge. Near where you would have fought the fishmen raiding party.

Hope this helps.

Alright, thanx for the answer to number 1.
I've stood there waiting for Solaufein for ages but he won't appear. I've tried waiting near the bridge and also at the very edge of the map... I raided the fisherman long before I got my drow disguise. Could this have affected something?

Damn, I'm not allowed to edit my own reply. Anyway, I meant to say thanx for your answer to question no 2...