Hi undergrd, it only happens for the tokina lens. The rest of the lens are fine, am having a 15-85mm and a 70-200mm 2.8 and when i depressthe shutter half way, the view in the view finder goes from blur to sharp, the usual. But only with the tokina, its blur and when i press half shutter, its still blur, but the pics comes out sharp.
Does the issue you mention only occur for this lens or all your lenses? You might want to check your diopter adjustment...