Thread:Project:Support desk/help with this: Fatal error: mcrypt create iv()/reply (27)

I got this error on my Windows 2003 system when I upgraded to MediaWiki 1.19.1 (from MediaWiki 1.18.0) with these components:
 * IIS 6
 * FastCGI 1.5
 * PHP 5.3.3 (Non Thread Safe VC9)
 * PostgreSQL 9.0.0-1

The error was resolved when I upgraded to PHP 5.3.16 (Non Thread Safe VC9).