Its really wierd, when i run Adobe Photoshop CS on my mac and i open up a render, it opens the the render isnt shown its just some black and white fuzzy thing appears its like in television when you switch to a wrong channel and all the fuzzy thing appears. EDIT:This thing happens when i open my renders in .png format
Did you download your photoshop? If so, a file might be corrupted. Or, during set up... you unchecked the .png format.