Hi Benny,
I had exact the same problem and I just downloaded the start of level 5 and went on with that one. But now I have the answer.
Go to
http://support.lucasarts.com) and download patch 1.2. When you downloaded it, look for it, click on it and it will find your game and install itself. Than go to your last saved game before entering the "icepalace" and start playing that part over. I ensure you it will come down and scears the hell out of you. If it not works, mail me and I will send you a saved game just after breaking the ice after killing icemonster. For now, try the patch. Succes!
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