PHP Extensions in Win32

I'm using php_ldap.dll (PHP 4.2.2 on WIN2k/IIS) and had a strange thing happen today. The server suddenly stopped answering requests with an error "Invalid Credentials". When I went to the server there were several pop-up windows visible all of which saying "cannot load module php_ldap.dll file not found" ... now the file was where it belonged and the credentials were fine. I checked the server for the PHP process and it wasn't there, but it refused to work correctly, just kept saying "Invalid Credentials". After rebooting the server it worked fine again. Has anyone seen this behavior before? Today was perhaps the most load the application has gotten since development. My theory is the file became in use and couldn't be used for subsequent calls giving the pop-ups. I have no clue why it would not work ever after though. Since that I was motivated to implement an AD cache mechanism that cuts down on the use of the ldap calls & hopefully I will not see this happen again. <>< Ryan