Rename the project directory Intel XDK is trying to open when it starts. Create a new project based on one of the demo apps. Test Intel XDK using that demo app. If everything works, restart Intel XDK and try it again. If it still works, rename your problem project folder back to its original name and open Intel XDK again (it should now open the sample project you previously opened). You may have to re-select your problem project (Intel XDK should have forgotten that project during the previous session).
Move your index.html and other source and asset files to the "www" directory you just created -- this is now your "source" directory, located inside your "project" directory (do not move the<project-name>.xdk and xdke files and any intelxdk.config.*.xml files, those must stay in the root of the project directory)