Mysql being killed on and off
 

As title says Mysql is being killed on and off,
we fund that wait_timeout=

is 10 ,
we set it to 180 , could you please advise if these errors could possibly be fixed with this update

mysql_connect() [function.mysql-connect]: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
/xxxxxx/xxxxxxx/public_html/xxxxxxx/includes/class_core.php on line 311


and

Database error in vBulletin 3.8.1:

Invalid SQL:

SELECT COUNT(*) AS count
FROM forum_attachment
WHERE posthash = '432b076d6c5b83edf0b80c6050645796'
AND userid = 48965;