Unknown MySQL server

[محروم.كوم]

Recently I keep getting notified of this error:

Quote:
Database error in vBulletin :

mysql_connect() [function.mysql-connect]: Unknown MySQL server host 'mysql50.wc2' (1)

/path/www.mysite.com/forum/includes/class_core.php on line 311

MySQL Error :
Error Number :
Request Date : Wednesday, March 17th 2010 @ 02:57:44 PM
Error Date : Wednesday, March 17th 2010 @ 02:57:54 PM
Script : http://www.mysite.com/forum/register.php?do=register
Referrer : http://www.mysite.com/forum/register.php?
Username :
Classname : vB_Database
MySQL Version :

Clearly this isn't an unknown server, or my whole forum would be down. Checked with my host, they said there is no problem there. What can I do to fix this? __DEFINE_LIKE_SHARE__