Apache error fix?

How can I fix this error which shows at the top of all my pages?

Warning: preg_match() [function.preg-match]: Compilation failed: missing ) at offset 24 in /home/genuine/public_html/wp-includes/class-wp.php on line 198

Warning: preg_match() [function.preg-match]: Compilation failed: missing ) at offset 24 in /home/genuine/public_html/wp-includes/class-wp.php on line 199

Warning: preg_match() [function.preg-match]: Compilation failed: missing ) at offset 24 in /home/genuine/public_html/wp-includes/class-wp.php on line 198

Warning: preg_match() [function.preg-match]: Compilation failed: missing ) at offset 24 in /home/genuine/public_html/wp-includes/class-wp.php on line 199