A HTTP 500 error amy be displayed when navigating to the Sage CRM login screen after installing on Windows Small Business Server 2011. This issue is caused by ASP.NET ISAPI extensions installed on the default website.


On navigating to the CRM login page, the following error message is disaplyed:

HTTP Error 500.0 – Internal Server Error
Description: Calling GetProcAddress on ISAPI filter “C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll” failed.
Error Code: 0x8007007f

A similar error is logged to the Event Viewer logs.


This issue is caused by the presence of two ISAPI filters (actually extensions) installed on the default web site.


Under Default Web Site | IIS | ISAPI Filters, remove the ASP.Net_2.0.50727.0 and ASP.Net_2.0_32bit entries.

ISAPI extensions 

More information:

If the logged error refers to an x64 path, then the CRM application pool should be set to run in 32-bit mode.

These filters may be required for another application installed into the same website on the SBS server. Since ISAPI filters are applied globally, the application requiring these filters should be isntalled into a separate website on the server.