(note: this should be under SOA, even if you have TOB installed)
have you installed patches? also, use search, it is a VERY useful tool. i found a thread that might help you. i got to it by going to the search, clicking on advanced search, put Rift dungeon (spelling is important) in the keywords area, then choos Baldurs Gate II: Shadows of Amn. there are a few posts but it only takes a few seconds to scan each thread.
this is the thread i found for you, make sure you read the entire thread...
here