MySQL too many connection problems

Hi folks-- I'm working on an installation of phpshop 0.6x and have started getting "too many connections to the database" errors whenever I work with it for any length of time. I have a heavily database-driven and busy site calling on three databases. Having heard that mysql_pconnect is better to use than mysql_connect, I thought maybe my other scripts using the latter were causing the problem so I moved the busiest pages from mysql_connect to mysql_pconnect. No go. The problem only occurs when I'm using phpshop and affects the entire site, not just the phpshop pages. Sometimes loading my (non-phpshop) home page restarts things, sometimes I have to go in and reboot mysqld. I have customized the phpshop code but I haven't done any customization to the way phpshop connects to the database. Ideas? Many thanks, Lynn