Just take over a web site, I will not play with Linux, more do not understand the mysql and PHP, not mysql statement, can only use simple search a table SQLyog, were forced to find problems, bitter ah, everyone passing by gods help,

2015 do shopping website, now unable to login, tip Error is: Db Error: database connect failed
Login shopnc background, account login password input point, also hint Db Error: database connect failed

Shopnc version is: shopnc B2B2C electric business platform system version 2015.06
WDCP Linux system can log in, the version is wdcp_v2. 5.15 (20150826)
Linux version of CentOS release 6.5 (Final)
Mysql version v5.1.69
As well as apache and nginx, too complicated, I don't understand,
Above these account password is complete,

Now there is a phenomenon may help debug,
In the/etc/my CNF in
[mysqld]
Skip - grant - tables
To join this one, the website can open, commented, it won't open, feel is a problem of mysql, but it is true that I am layman,

Please give some solution? Thank humbly.