I have a v1.1.4 application that works fine locally with IIS7 and php 5.3.2 but when I deploy it under php 5.2.6 and IIS7 I get the 500 - Internal server error for the pages that use widgets.
Never used IIS but i guess even Microsoft will deliver their webserver with some logging capability . So check out the webserver’s error log file. It should give you an idea where to search for the problem.
I digged by changing code in the framework and I found that most widgets are using AssetManager to publish scrips from web/js/source to the application ‘web accessible directory’.
So all I had to do was to give the IIS user full rights to the (basePath)/assets directory and subdirs.