Horde webmail error 502

[ralphb]

Hi all,

I'm receiving an error when i try to connect to Horde webmail.
Windows server 2008 iis7 Plesk 8.6
error:
502 - Web server received an invalid response while acting as a gateway or proxy server.
There is a problem with the page you are looking for, and it cannot be displayed. When the Web server (while acting as a gateway or proxy) contacted the upstream content server, it received an invalid response from the content server.

I've found the following article.
http://techsupportoncall.blogspot.com/2008/08/horde-error-502-web-server-received.html

Strangely enough; php_fileinfo.dll, php_mysql.dll and bphp_mysqli.dll do not appear to exist in the php.ini.

Can anyone help me.