That's normally speaking a bug that's patched in the latest patches, even if they don't mention it. Does it say that the chars "don't have anything to say to you"? Then it shoudl be solved with the patches.

Yeah it's a common problem with BG2, the patch now though is pretty much perfect and fixes all known problems within the game

I used to have links to them in my signature, but since we don't get many newbie's they weren't really in demand anymore