Visit thread where the same issue is discussed by CorelDraw pros: http://community.coreldraw.com/talk/.../f/704/t/43936

If resource above didn't help, you would need to identify what may have caused the file corruption. Possible causes could include:
• Document was corrupted / not saved due to the program crashing or hanging
• Saving large files to a network drive.
• Documents created in earlier versions of CorelDraw® are no longer accessible