Warning: file_exists() [function.file-exists] - Joomla! Forum - community, help and support

hello. joomla website has been working fine several years. suddenly, has begun displaying strange error message. furthermore, cannot log joomla administrator/backend. can me ?
the error message follows:

warning: file_exists() [function.file-exists]: open_basedir restriction in effect. file(c:\inetpub\vhosts\nobcouncil.com\httpdocs\installation\index.php) not within allowed path(s): (c:/inetpub/vhosts/nobcouncil.com\;c:\windows\temp\) in c:\inetpub\vhosts\nobcouncil.org\httpdocs\includes\framework.php on line 27

warning: session_start() [function.session-start]: cannot send session cookie - headers sent (output started @ c:\inetpub\vhosts\nobcouncil.com\httpdocs\includes\framework.php:27) in c:\inetpub\vhosts\nobcouncil.com\httpdocs\libraries\joomla\session\session.php on line 423

warning: session_start() [function.session-start]: cannot send session cache limiter - headers sent (output started @ c:\inetpub\vhosts\nobcouncil.com\httpdocs\includes\framework.php:27) in c:\inetpub\vhosts\nobcouncil.com\httpdocs\libraries\joomla\session\session.php on line 423

warning: cannot modify header information - headers sent (output started @ c:\inetpub\vhosts\nobcouncil.com\httpdocs\includes\framework.php:27) in c:\inetpub\vhosts\nobcouncil.com\httpdocs\libraries\joomla\session\session.php on line 426

thanks in advance help.

can access via front-end?

you can open file 'configuration.php', find error report , set none, warning disabled.