Php warnings causing site to b-o-g down

Can someone explain how to stop the following errors:

[10-Nov-2009 04:37:24] PHP Warning:  Module 'pdo_mysql' already loaded in Unknown on line 0
[10-Nov-2009 04:38:05] PHP Warning:  Module 'PDO' already loaded in Unknown on line 0
[10-Nov-2009 04:38:05] PHP Warning:  Module 'SQLite' already loaded in Unknown on line 0
[10-Nov-2009 04:38:05] PHP Warning:  Module 'pdo_mysql' already loaded in Unknown on line 0
[10-Nov-2009 04:40:15] PHP Warning:  Module 'PDO' already loaded in Unknown on line 0
[10-Nov-2009 04:40:15] PHP Warning:  Module 'SQLite' already loaded in Unknown on line 0
[10-Nov-2009 04:40:15] PHP Warning:  Module 'pdo_mysql' already loaded in Unknown on line 0
[10-Nov-2009 04:40:15] PHP Warning:  Module 'PDO' already loaded in Unknown on line 0
[10-Nov-2009 04:40:15] PHP Warning:  Module 'SQLite' already loaded in Unknown on line 0
[10-Nov-2009 04:40:15] PHP Warning:  Module 'pdo_mysql' already loaded in Unknown on line 0
[10-Nov-2009 04:40:19] PHP Warning:  Module 'PDO' already loaded in Unknown on line 0
[10-Nov-2009 04:40:19] PHP Warning:  Module 'SQLite' already loaded in Unknown on line 0
[10-Nov-2009 04:40:19] PHP Warning:  Module 'pdo_mysql' already loaded in Unknown on line 0
[10-Nov-2009 04:41:10] PHP Warning:  Module 'PDO' already loaded in Unknown on line 0
[10-Nov-2009 04:41:10] PHP Warning:  Module 'SQLite' already loaded in Unknown on line 0
[10-Nov-2009 04:41:10] PHP Warning:  Module 'pdo_mysql' already loaded in Unknown on line 0