Correct, the unofficial patch.
I've tried from the steelfury.info site (gets to 19.5 MB downloaded and sits there, never finishing or progressing) and Mediafire (gets to 19.5 Mb downloaded and finishes).
I just tried again and got the same error. I can actually run the .exe and extract files (from all download attempts), and it works until the file I mentioned before, basic_physics.codelib.
This occurs on two computers, one with XP and one with Vista.