Some possibilities:
1) Your documents use a font that is missing or corrupt. Try selecting the
entire document and choose another font. If the text is now readable,
reinstall the missing/corrupt font.
2) You've opened the document with the wrong setting in the 'Files of type'
list on the File > Open dialog. Eg, you've opened the document as plain
text.
> Has anyone ever had any problems with Microsoft Word documents filling
> with unreadable boxes and all of the text disappearing? My journals
[quoted text clipped - 5 lines]
>
> - Adam Rumpke