Text Disappearing in Preview Mode

I am creating a newsletter for a non-profit currently and have been working on it for a couple weeks. Today though, I was switching my screen mode from Normal to Preview and some of my text was disappearing. Not completely though...I could still highlight the text in the boxes, I just can no longer see it. But when I switch from Preview back to Normal the text re-appears. Anyone else having this happen and do you have any solutions or suggestions? Thank you!