The Kindle only has about 600 x 800 pixels to display stuff, so it is limited in what it can display. Try resizing your images to be closer to what the Kindle can display. Some things are too complex to display in that small a resolution.
iroar, I assume you're referring to graphics in books you've purchased, but you didn't specify. Have you tried moving the cursor (using the 5-way controller) over the graphic, to see if it can be resized? That often helps, especially if the graphic wasn't full-size to begin with. When your cursor is over the graphic, you'll see a magnifying glass icon with a plus sign in the middle. Just click the center button on the 5-way and the graphic may enlarge.
This will work in .mobi, .prc, and .azw (Amazon) books, but not in .pdf files.
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