Very frustrating image import issue - please help

I have downloaded several hi-res images, most of which are 4256 x 2832 and when I pull those images into photoshop, they appear pixelated and of horrible resolution, even though when I open them in a simple image viewer they look great. 

I've been scouring other forums and using some of the other suggestions seen, but I cannot figure this out. I've tried...

- Uninstalling/reinstalling

- Deleting user preferences

- Changing Image Interpolations

- Clicking on/off "Resize Image During Place"

I am at a total loss here and I cannot use photoshop for an urgent project I have. This is really frustrating. If anyone has real suggestions, please let me know. I know the question will come up of showing pictures of this, but I cannot show them due to the privacy of the project I am working on. Like I said, the hi-res image is appearing pixelated and of very poor quality when dragged into photoshop.