wordpress membership plugin install waring

I installed wordpress membership plugin. then it shows warning.

Warning: fopen(/home4/ricktews/public_html/wp-content/plugins/membership/membership.php) [function.fopen]: failed to open stream: No such file or directory in /home4/ricktews/public_html/wp-includes/functions.php on line 4165
Warning: fread(): supplied argument is not a valid stream resource in /home4/ricktews/public_html/wp-includes/functions.php on line 4168
Warning: fclose(): supplied argument is not a valid stream resource in /home4/ricktews/public_html/wp-includes/functions.php on line 4171
Why does it show waring?
Please help me