Okay, apparently I haven't explained the problem correctly.
I've been using LR since LR2, and I've never had this problem before.
When I am in the Library Module, there is a bar across the bottom of the page. This bar has several features, but the ones I'm having problems with are the "stars" and the "colors" (red, yellow, green, blue, purple). Formerly, if I selected a thumbnail or a group of thumbnails and moused over the star or color, I could left click on of the star or color to rate the image. Now, when I click on a color or star, the thumbnail does not show the star rating, or the color. In addition, if I select a thumbnail or thumbnails, and try to do star or color ratings with the numeric keypad, I have the same problem ... the rating or color does not appear on the thumbnail. I have always been able to use either method in the past ... this is a recent problem, so I am curious if anyone else has the problem, and whether they have found a solution.