Hi,
That usually happens when you've chosen a text Background-Color (or any other Font code or style setting) in the HTML for the description text. Copy and paste of code will often pick-up and embed unintended settings too.
Switch the description editor to HTML mode to locate them. You can also select all the text in the Standard View and use the "eraser tool" on the toolbar to remove all Format codes and leave only the plain text.
Danno