I have found a bug on PPM when you login and go to the New Posts SInce Last visit link i get this:

Could not insert search results

DEBUG MODE

SQL Error : 1062 Duplicate entry '791497360' for key 1

INSERT INTO ppmhix_search_results (search_id, session_id, search_array) VALUES(791497360, '70de347a11edd75fcacd31e11d6e64e8', 'a:7:{s:14:"search_results";s:4:"9068";s:17:"total_match_count";i:1;s:12:"split_search";N;s:7:"sort_by";i:0;s:8:"sort_dir";s:4:"DESC";s:12:"show_results";s:6:"topics";s:12:"return_chars";i:200;}')

Line : 727
File : search.php