2.5RC1 login problem

Hello ppl!I just installed 2.5RC1 and after the install when i go to login and fill my username and pass, i press login and i have an error page saying
“Warning: getmypid() has been disabled for security reasons in /myservername/myusername/public_html/blog/wp-includes/class-phpass.php on line 51

Warning: Cannot modify header information – headers already sent by (output started at /myservername/myusername/public_html/blog/wp-includes/class-phpass.php:51) in /myservername/myusername/public_html/blog/wp-includes/pluggable.php on line 556

Warning: Cannot modify header information – headers already sent by (output started at /myservername/myusername/public_html/blog/wp-includes/class-phpass.php:51) in /myservername/myusername/public_html/blog/wp-includes/pluggable.php on line 693

Any opinion?
Thanks in advance!