Error: too many connections

Need help with this error.
The PHPRunner-generated PHP applications have been running fine until yesterday when this error occured.
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PHP error happened
Technical information

Error type: 2

Error description: mysql_connect() [function.mysql-connect]: Too many connections

URL: www.mydomain.com/xxx/xxx_list.php?

Error file: web:/xxx/xxx/include/dbconnection.php

Error line: 9

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Have asked the system administrator to restart the MySQL server but the errror retains. He also asked whether I have included mysql_close() scripts in each connection action. I simply check the dbconnection.php and it seems that the scripts are there (I have no knowledge about PHP). Could anybody give suggestions? Thanks.