I hope you have imported the photos.
What happens when you double-click? Does it get displayed correctly?
Does this happen with all the images you imported?
Yes, when I double click I can see them but unless I am clicked on the photo - all thumbnails stay gray and unseeable
You either have a defective monitor profile, in which case the answer was given by dj_paige above,
or you have a corrupted preview cache, and have to delete it.
With Lightroom closed, use Windows Explorer/Mac Finder, and go to the folder that contains the Lightroom catalog. The folder is normally named Lightroom, and is usually located inside the Pictures or My Pictures folder.
Delete the folder whose name ends with Previews.lrdata. (on a Mac this folder may appear as a file) Do not delete anything else.
Now launch Lightroom, and the previews will rebuild as you browse the Library.