Lightroom :: 4.4 / Only 3 Thumbnails Will Display At A Time In Both Grid View And Film Strip

I have Lightroom 4.4. and Windows 7--both of which have been working fine for several months. Starting a few days ago, however, thumbnails have refused to load for any NEW photos I import. They appear gray/blank in both Grid view and the film strip. However, if you click on any of the film strip thumbnails (while in either Grid view or Develop mode), that thumbnail and corresponding image WILL load--until up to three have done so. Then they begin disappearing again, allowing you to view no more than three images' thumbnails at any one time.
 
I can't review a shoot via Grid mode this way. I'm also afraid to use Lightroom while it's misbehaving, for fear of corrupting the catalog somehow (though all the images appear to be there). Searching this forum, I found several people who experienced having all of their thumbnails blank out and who were able to correct this by either reinstalling or removing their color profiling software. However, 1) I did this (and it didn't work), and 2) it isn't that all my thumbnails that have disappeared. All the thumbnails and images imported prior to the bug, still initially display correctly.* And I can get three thumbnails of the newer images to appear at a time.
 
*The asterisk is because after I poked around some more, I realized that if I opened other folders and began post-processing images from older uploads (vs. just viewing them), the thumbnails that initially displayed correctly everywhere also blank out and begin appearing in this up-to-three-at-a-time fashion.