Attention: OpenPublish requires PHP version 5.2.x. Drupal is not compatible with 5.3 and modules used in OpenPublish are not compatible with 5.1.x. Please, also, make sure PHP has enough memory to run Drupal installation. Your memory_limit variable, in php.ini needs to be at least 64M, but 128M is highly recommended. If you are still having problems (seeing "white screens of death" or errors during installation) try setting max_execution_time to around 120 and realpath_cache_size to 512K, 1M or even 2M.
Changes from 1.5 to 1.6: