When you open the IGS file with Solidworks 2006, it does an import. Then it asks if you would like to check for faults and gaps. If you say yes then it goes through and checks. It comes up with quite a few faults and gaps. I managed to erase the sight rail off the back of the marker which seemed to be causing most of the problems.
On another note: Stock Eye Tab for B2K4 w/PDS (I also have a .dwg for it)