Using mysql_pconnect instead of mysql_connect can cause serious issues on high volume servers.
Read all the notes at php.net and Persistent Database Connections before enabling persistent connections. What often happens is that a whole lot of connections get locked and MySQL runs out of available connections. This occurs with Pear’s DB too. LoadRunner doesn’t always catch this error.
This is a known bug: Bug #7634 mysql_pconnect() + lock tables can hang server
Immediately logged out after loggin in
Just a simple note. If your web page logs you out immediately after logging in, check your system clock (esp on the apache and MySQL (SQL) server.