Urgent Help! I have an open file that is frozen - out of memory + other strange warning

Hi there, I've been working on an image for about 4 hours... (PHOTO PAINT X4) The screen is now frozen with a small box saying ''out of memory'' I haven't saved the file for a few hours - oh the pain of it! Can anyone help me? Or has all this work now gone. I now also have this message with no text, does anyone know what it might be and which button I should press!? Or is there some sort of shortcut to save. Thanks in advance.