os: win2000 advanced server
web server: IIS 5 + ISAPI PHP 4.0.3pl1
db server: MS SQL 7 (same machine)
used script:
<?php
  $conn = mssql_pconnect("sername","test","test") or die("error when connecting");
  $db = mssql_select_db ("Northwind", $conn) or die("error when selectin db");
?>

error msg: 
PHP has encountered an Access Violation at 73342F43

When I press Refresh in IE, in 50% results it's ok and in 50% I get that error message. If I change 'pconnect' to 'connect', no error apperars.

When I try Apache (module or cgi) instead of IIS, everything is ok.