If thumbnails of files which should be importable aren't displayed in import dialog box, then problem may be monitor profile:
If not applicable, perhaps you could provide a little more info..
I have tried this and doesn´t work.
I´m going to try to explain it better.
1.- I open lightroom
2.- I create a new catalogue
3.- i go to import screen
4.- I select a picture folder
5.- The thumnails doen´t appear in the middle of the screen and the import button is gray (i can not import the pictures). Is as doen´t exists