MySql has exceeded the 'max_user_connections' error

Recently my web site has been throwing a -

my sql has exceeded the 'max_user_connections'

error. I've checked my code and believe I'm closing all open connections when I should do. After running the 'SHOW PROCESSLIST' command it lists a number of processes where the state is 'sleep' and the 'info' is null, similar to this Stack Overflow question -

http://stackoverflow.com/questions/...list-lists-many-processes-sleep-and-info-null

Is there anything I can do either in the databsae set-up in the control panel or in my connection string that will prevent MySql hanging on to processes? My connection string currently looks like this -

server=server;User Id=user;password=****;Persist Security Info=True;database=mysql5_867860_footytriv;Pooling=true;Min Pool Size=10;Max Pool Size=15