Do you get an HTTP error when you upload pictures? I used to get an HTTP error at first, but after reloading the page, the pictures would be in the Media Library anyway. But, when I tried to put them in the page, they wouldn’t show up either.
So, I checked the code (TEXT) background tab and noticed that all the new images I’d put in (that delivered the HTTP error) were being shown at 1px height and 1px width. You might check that on yours as well. I simply reset the height and width to what I wanted and it worked.
Check the code portion of your post or page to see if the images are actually being put in or not.
