Win/IE doesn't do so hot with images that are embedded in <LABEL> elements. There are a couple of possible solutions to the problem.

Option 1 — Behavior

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label img {
  behavior: url({path_to_behavior}label_img.htc);
}

For you validation sluts, you can, alternatively, place the image as a background on the <LABEL> elements. However, this will bring up a whole slew of positioning issues if you're placing the <INPUT> element for the checkbox or radio button inside the <LABEL> element.