Sorry if you already answered that Koja, I think I was looking at an old
reply.

-OK, click on the little pull down menu for the Quick Access Toolbar
-choose more commands
-on the right under your toolbar window, click the reset button (this will
undo all of your cutomization, sorry)
-click ok.
-make sure the Quick Access Toolbar has only the 3 (I think its 3) default
icons
-exit word, reopen word
-create a new table as a test, and try to get it to darken the cells again.

Let me know what happens!

JT