less on iis not working

问题:

I use less with the dotless dll downloaded from

http://www.dotlesscss.org/

I have added to web config all references suggested by the site

<add type="
    dotless.Core.LessCssHttpHandler
    ,dotless.Core" validate="false"
    path="*.LESS" verb="*" />

<section name="dotless"
    type="dotless.Core.configuration.
    DotlessConfigurationSectionHandler
    ,dotless.Core" />

When i run the application with visual studio development server on my pc all works fine. When i run the application with local IIS there is an error

GET .../myapplication/Styles/SiteLess.less 500 (Internal Server Error)

there is another settings on iis 7.5?