Unexpected PHP Errors

These are the errors I’m getting:

Warning: preg_match() [function.preg-match]: Compilation failed: nothing to repeat at offset 1 in /home/nc/public_html/wp-includes/class-wp.php on line 202

Warning: preg_match() [function.preg-match]: Compilation failed: nothing to repeat at offset 1 in /home/nc/public_html/wp-includes/class-wp.php on line 201

Just lines and lines of that, and at the end it says:

Warning: Cannot modify header information - headers already sent by (output started at /home/nc/public_html/wp-includes/class-wp.php:201) in /home/nc/public_html/wp-includes/functions.php on line 861

Warning: Cannot modify header information - headers already sent by (output started at /home/nc/public_html/wp-includes/class-wp.php:201) in /home/nc/public_html/wp-includes/functions.php on line 862

This happens when I click on the Pages tab in my WordPress administration panel. I’m pretty sure I don’t have any corrupt files and I have tried reinstalling my version of WordPress numerous times but I still get the same error. Does anyone have a fix for this?