I’d started to deploy a test version of SugarCRM 5.5 CE and an updated PHP 5.2.12 to a Windows 2008 server with IIS7 when I got an internal server error 500.

What I found, eventually, was that while the installation of Sugar completed, the installation creates a web.config file that includes an instruction to ‘Add default document type’ of index.php to the site.

The problem was that my server level settings already included index.php as a default document. The only reason I found it was when checking all the settings for the site in the IIS7 Manager it gives an error in the manager about the double up not being possible.

Would have been more polite if IIS could simply accept that the index.php already is a default document and ignore it politely instead of doing a dummy spit type error and not running.

In this case I just deleted the instruction to Add in the web.config.

Another option is to include a instruction in the web.config to clear any existing default pages prior to adding the one(s) required for the current application. Like this:

Logged as a Bug at Sugar BugTracker