2.0 Errors

Warning: preg_match() [function.preg-match]: Compilation failed: unrecognized character after (?< at offset 5 in /home/birche5/public_html/CarolHomeStaging/wp-content/plugins/nextgen-gallery/products/photocrati_nextgen/modules/router/class.routing_app.php on line 484

All over my website after upgrading to the new gallery. I have defaulted the theme, and disabled all other plugins…no luck.

http://wordpress.org/plugins/nextgen-gallery/