Error 500 editing emails accounts and viewing services

[docilweb]

My server is running Plesk 11.0.9 MU#38 on Linux CentOs 6. When I go to Setup & Tools --> Services management, Plesk gives Error 500.

/var/log/sw-cp-server/error_log:

2013-03-07 10:05:49: (mod_fastcgi.c.2613) unexpected end-of-file (perhaps the fastcgi process died): pid: 1256 socket: unix:/usr/local/psa/tmp/sw-engine.sock-0
2013-03-07 10:05:49: (mod_fastcgi.c.3400) response not received, request sent: 2019 on socket: unix:/usr/local/psa/tmp/sw-engine.sock-0 for /plesk.php?, closing connection

Also when I try to edit an email account:

2013-03-07 10:20:25: (mod_fastcgi.c.2613) unexpected end-of-file (perhaps the fastcgi process died): pid: 4624 socket: unix:/usr/local/psa/tmp/sw-engine.sock-0
2013-03-07 10:20:25: (mod_fastcgi.c.3400) response not received, request sent: 2242 on socket: unix:/usr/local/psa/tmp/sw-engine.sock-0 for /smb/index.php?, closing connection