No X button on App Store downloaded apps icons in Launchpad "jiggle mode" I can't seem to uninstall Mac App Store purchased applications.

I know that holding down the Option key or clicking and holding on the app icon to make the icons start jiggling so you can uninstall the app by clicking the “X” shown in the corner of icons only works for apps downloaded from the Mac App Store.

But I my case, not even apps downloaded from the Mac App Store show the "X" button when in jiggle mode.

Has anyone experienced the same problem ? How did you solved it ?

UPDATE:
When I delete the app from the Finder, the app's icon remains in the launcher, undeletabe, only it doesn't find the missing app.
You don't have to use Launchpad to remove applications. Just deleting the application bundle is still a supported way to remove or uninstall an application. If you also want to remove settings or cache files, delete the directory in ~/Library/Containers/. App Store applications are not allowed to install kernel extensions or preference panes, and any executables for helper processes are inside the application bundle and not in an Application Support directory.

When you remove an application from Launchpad, it is "uninstalled" by using uninstalld from Uninstall.framework, but in practice that only removes some support files (like ~/Library/Containers/*/Data/Library/Caches/) addition to the application bundle. Other support files like preferences files or sometimes even sqlite files for user data are not removed. See this question.