The issue with mine was that I created a Virtual Directory in which the Parent Website had a wildcard mapping for all files to go to aspnet_isapi.dll. When you create a new vitual directory it inherits the default settings of the parent website. You then need to go to DNN virtual directory and remove the wildcard mapping. The following are the steps that i used to get it working.

1. In IIS Right Click on website/virtual directory
2. In the popup context menu click properties
3. Click on the "Home Directory" tab
4. To the right of the "Starting Point" or "Execute Permissions" click on the "Configuration..." button.
5. In the second (bottom) list box called "Wildcard application maps" remove any wildcard maps. I removed all of them for DNN. (I only had 1 mapping)
6. Click "OK"
7. Click "OK"
8. Click "OK"