Possible solutions of your questions

Hello. after some changes to the website stopped working and it worked, does it?

error

[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Warning: include_once(/var/www/coblov/data/www/ecatelena-plast.com.md/components/com_jcomments/jcomments.legacy.php): failed to open stream: No such file or directory in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 78
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Warning: include_once(): Failed opening `/var/www/coblov/data/www/ecatelena-plast.com.md/components/com_jcomments/jcomments.legacy.php` for inclusion (include_path=`.:/usr/share/php:/usr/share/pear`) in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 78
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Notice: Use of undefined constant JCOMMENTS_BASE - assumed `JCOMMENTS_BASE` in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 106
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Warning: include_once(JCOMMENTS_BASE/jcomments.class.php): failed to open stream: No such file or directory in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 106
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Warning: include_once(): Failed opening `JCOMMENTS_BASE/jcomments.class.php` for inclusion (include_path=`.:/usr/share/php:/usr/share/pear`) in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 106
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Notice: Use of undefined constant JCOMMENTS_BASE - assumed `JCOMMENTS_BASE` in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 107
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Warning: include_once(JCOMMENTS_BASE/jcomments.config.php): failed to open stream: No such file or directory in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 107
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Warning: include_once(): Failed opening `JCOMMENTS_BASE/jcomments.config.php` for inclusion (include_path=`.:/usr/share/php:/usr/share/pear`) in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 107
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Notice: Use of undefined constant JCOMMENTS_HELPERS - assumed `JCOMMENTS_HELPERS` in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 108
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Warning: include_once(JCOMMENTS_HELPERS/system.php): failed to open stream: No such file or directory in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 108
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Warning: include_once(): Failed opening `JCOMMENTS_HELPERS/system.php` for inclusion (include_path=`.:/usr/share/php:/usr/share/pear`) in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 108
[Thu Dec 25 23:56:59 2014] [error] [client IP] PHP Fatal error: Class `JCommentsSystemPluginHelper` not found in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 112
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Warning: include_once(/var/www/coblov/data/www/ecatelena-plast.com.md/components/com_jcomments/jcomments.legacy.php): failed to open stream: No such file or directory in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 78
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Warning: include_once(): Failed opening `/var/www/coblov/data/www/ecatelena-plast.com.md/components/com_jcomments/jcomments.legacy.php` for inclusion (include_path=`.:/usr/share/php:/usr/share/pear`) in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 78
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Notice: Use of undefined constant JCOMMENTS_BASE - assumed `JCOMMENTS_BASE` in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 106
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Warning: include_once(JCOMMENTS_BASE/jcomments.class.php): failed to open stream: No such file or directory in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 106
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Warning: include_once(): Failed opening `JCOMMENTS_BASE/jcomments.class.php` for inclusion (include_path=`.:/usr/share/php:/usr/share/pear`) in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 106
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Notice: Use of undefined constant JCOMMENTS_BASE - assumed `JCOMMENTS_BASE` in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 107
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Warning: include_once(JCOMMENTS_BASE/jcomments.config.php): failed to open stream: No such file or directory in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 107
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Warning: include_once(): Failed opening `JCOMMENTS_BASE/jcomments.config.php` for inclusion (include_path=`.:/usr/share/php:/usr/share/pear`) in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 107
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Notice: Use of undefined constant JCOMMENTS_HELPERS - assumed `JCOMMENTS_HELPERS` in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 108
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Warning: include_once(JCOMMENTS_HELPERS/system.php): failed to open stream: No such file or directory in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 108
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Warning: include_once(): Failed opening `JCOMMENTS_HELPERS/system.php` for inclusion (include_path=`.:/usr/share/php:/usr/share/pear`) in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 108
[Thu Dec 25 23:57:04 2014] [error] [client IP] PHP Fatal error: Class `JCommentsSystemPluginHelper` not found in /var/www/coblov/data/www/ecatelena-plast.com.md/plugins/system/jcomments.php on line 112

you did backup before upgrading?

the error indicated that nanadana files

JCOMMENTS_HELPERS/system.php

restore the site from backup and try again to update , it seems that not all files were updated

OK