Membership Plugin Errors

Installed the plugin, followed the steps to set the plugin. after creating pages for registration page, no access page i get this error.

Warning: preg_match() [function.preg-match]: Unknown modifier 'T' in /home/***/public_html/wp-includes/class-wp.php on line 199

Can't figure out from where the error comes from.
Deleting the pages make this error disappear.

triyed everything. Nothing works. When creating page and choosing it in Memership plugins option, The error appears.
Tried to dissable all plugins to see if there is any conflicts. Not helps.
Using latest version 3.1.3 of wordpress/

What to do?