Ubuntu :: Contents Of Text Documents Displayed In Their Icons?

but not all, of my text documents show their contents as their icons, instead of using my theme's designated icons for text files. For example, in the above image, the bottom-right file contains: "hello ubuntu forums / this is my problem / how can we fix it? / thank you" and it's icon displays some of this message so that it may be read without opening the file As you can see, the problem occurs with some filetypes, like .txt and .html, but not with others, like .doc or .rtf. How can I force all text files to use my theme's designated icons?