Fatal error

Most of the time, when I try to save a post or a page, I get this message :

Warning: require(/home/mysite/public_html/wp-includes/load.php) [function.require]: failed to open stream: No such file or directory in /home/embouled/public_html/wp-settings.php on line 21

Fatal error: require() [function.require]: Failed opening required ‘/home/mysite/public_html/wp-includes/load.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/embouled/public_html/wp-settings.php on line 21

I searched the web and two possible solutions I found are :
1- Try re-uploading all files & folders – except the wp-content folder – from a fresh download //// (but because I used the hotsportal installation, I’m a afraid to lose data and settings)

2- Fatal error in the output generally indicates either your theme doesn’t like your version of WordPress, you have a plugin that doesn’t like your version of WordPress, or you have an incomplete install/upgrade. //// (I just moved from joomla to wordpress. Under Joomla, I used sportal for joomla and never had that problem. So could it really be a template issue ?).

Please help me out