I can't get my scenes saved properly

I’m relatively new to modelling, so I just started to model my first self-made prop. I don’t think I had some particular problem getting the shape done, since it was pretty basic, but I was a bit disappointed to see that my scene didn’t save correctly and could not open it after restarting my system. By inspecting closer I noticed almost all my saved scenes had the same problem.
What causes the scenes to break most of the time ?

[editline]20th February 2011[/editline]

I use Softimage 7.5, if it can help.