ArtRage studio Pro 3.5 shows error when opening files

Questions:
Hello,
I have ArtRage Studio Pro 3.5 installed on my laptop and all of a sudden I started having trouble opening the .ptg files. I was doing a drawing when ArtRage crashed and I was able to reopen the file and only had to redo some parts and saved the file. Again I had a crash and this time when I try opening the file, I get this error message shown in the below attachment. And there is absolutely nothing on the canvas. There were no color samples, layers or references present. I tried exporting the file, but this file was also blank. I am running Mac OS X 10.8.4 on my machine. I am really clueless as to how to recover my lost drawing. Please can anyone help in finding the drawing as well as reinstalling this software so that it doesn’t encounter such frequent crashes in future? I am new to digital art any other tips you can offer will be of immense value to me. Thanking everyone taking their time out on fixing this issue in advance.

Error:
An error occurred on attempting to read/write data from / to a fie stream.
File= Three muses Layer = 0
