Invalid .PRJ file
It has been my experience that if you run out of hard drive space
(and none of us do that :-)!) during a session and you save the
.prj file it is only partially saved and there is no error message
to allert you to the fact that there is'nt enough hard drive space
to completely save the file. Then if you rush out of the program and
miss the message that lets you know "you have unsaved changes are you
sure you want to exit?" you are screwed. You only have a partially
saved file.
-Lee