Fatal error : function.require-once

One fine day I received following message….I haven’t installed any plug-ins or changed anything.

Warning: require_once(/home/minist39/public_html/wp-config.php) [function.require-once]: failed to open stream: Permission denied in /home/minist39/public_html/wp-load.php on line 29

Fatal error: require_once() [function.require]: Failed opening required ‘/home/minist39/public_html/wp-config.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/minist39/public_html/wp-load.php on line 29

It does not allow me to log in to my dashboard.
What is the solutions for this? Any help would be much appreciated.
Thanks
Nilesh