http://bugs.winehq.org/show_bug.cgi?id=18101
--- Comment #12 from GyB gyebro69@gmail.com 2012-07-09 11:50:20 CDT --- Still present in Wine 1.5.8, tested with Icewind Dale 2 Complete. Just as in my previous test, the problem doesn't occur when I install the game on an external usb disk.
Out of curiosity (and mainly because both Icewind Dale and Baldur's Gate use the same Infinity game engine), I tried the patches in bug #17956 (attachment #40936 and attachment #40937). Guess what? The patches do fix the problem when creating a new party in IWD 2.