First thing: make sure you have no filter set:
Filters are "sticky" -- they remain in place for every container until you remove them. Note that the default filter -- "Unrated or better" -- excludes some Images that are in the container.
Message was edited by: Kirby Krieger
You may have accidentally typed a "9". This will reject images, and they are not displayed, if the searchfield in the Browser is set to the default "unrated or better" . Change this to "Show all" by clicking on the looking glass in the search field.
You can also view your rejected image in the "Rejected" album in the "Recent" section of the library.
To unreject the images change the rating to a different value.
Added: I see, Kirby alread solved it!