Someone has the problem on the french forum (http://forum.coppermine-gallery.net/index.php?topic=16647.0).
The problem I can see: in the toprated album, when some pictures have the same rating/number of votes, the sort order is not the same in thumbnails.php and displayimage.php. The concrete result is that when you click a thumbnail, it's not the good picture that comes.
Please check if http://forum.coppermine-gallery.net/index.php?topic=5653.0 or http://forum.coppermine-gallery.net/index.php?topic=7315.0 (and the links inside those threads) deal with the issue you're having.
Joachim
Thanks! Your first link was the good one...
It should work the best with "pid DESC" since it's unique (unlike filename).
I proposed it to the guy but it has to work... ;)