php_mysql library

hi there -- i need help badly -- i finally got the mysql library for php to work but now it will work for a few page loads and then all mysql/php pages produce a web server 500 error -- this is unrelated to programming as it doesn't matter what php script is running -- even the phpmyadmin panel. If I restart the web service, it runs fine a few pages then the 500 error. This is under windows server 2003 and IIS. Help! there weren't really installation instructions with the library so i'm guessing maybe i goofed up the installation somehow?