unable to connect to MySQL Or MySql is not Allowing more Connections

some times aborting connections or interrupting process lead to another problem to server from stop giving connections to client. that is
server do not allow any more connections to client.
probable causes would be.
client is idle more than wait_timeout or
due to long queries getting aborted from client or
client makes mistake in authentications while connecting to database.
all these lead to increase in aborted_client counter of server variable.

and if max_connect_errors= (default is 10) is set to very low will cause a server to give more connection to client when it goes beyond limit
so its better to set it something more (normally 5000-10000) which will minimize this error.

please see more ref. I found for same

http://dev.mysql.com/doc/refman/5.0/en/blocked-host.html
http://dev.mysql.com/doc/refman/5.0/en/communication-errors.html
http://lists.mysql.com/internals/33476