Can you go to the preferences and change it back to the default? Will that work?

Is it the document window where you pose that the background is black?  On the bottom right hand side of that window are two circles or dots, if I recall correctly. The circle on the left can change the background color. Just click on that and change it.

I learned that from Dr. Geep.

The only thing I don't procrastinate is procrastinating. That I do right away.