I've just tested again. Well, now they didn't match with the last uploads, but after the second click nothing happens. I waited 5,10,15.. 1min. Second click didn't work.
Maybe it is a browser problem? I use IE7 here. Will check with others now...
Actually, I can now see that the random images are the same even if I reload the page. I mean.. the first reload is ok, i see different pics, then I click and the previous randoms came back (the same as with the previous click before the reload)
Now I checked with IE6 on the other computer and the result is the same....