error reading a file upon opening

I have been a Corel user since the 3.0 version and never had this happen before.....I worked for hours and hours creating a poster, saved it, this morning, it won't open.  I get an "error reding file" message.  I can see the file in the thumbnail, tried dragging it onto the desktop, all the tricks I know, nothing works, same message.

 

HELP