There is a problem with memory handling in cpm_viewRandomMostViewedMediaFrom - that crops up in very large galleries.
(like 20,000 pictures).
It will basically result in an out of memory condition on your server.
I am working on a fix, but for now if you edit the cpmfetch_config.php file (in the dev releases) you can change the line that reads:
// What percentage will be evaluated as being top rated
// $config_overrides['cfTopPercentForTopRated'] = '10';
to something less... like
$config_overrides['cfTopPercentForTopRated'] = '2';
The same bug probably will occur with the random most viewed, the setting for that is in:
// What percentage will be evaluated as being most viewed
// $config_overrides['cfTopPercentForMostViewed'] = '25';
Vuud