Did your Nokia N9 home screen get broken after upgrading the operating system to Harmattan PR1.2 or PR1.3? Does it look like the image on the right, with the folder layout completely broken and the folder icon shown as a red rectangle? If so, your operating system files have been modified by a broken third party application - most likely a non-Store application called Home Screen Background Settings. (NOTE: The application is NOT to be confused with Home Screen Settings available from the Store. Home Screen Background Settings is broken, Home Screen Settings is not.)
To fix the problem,
The Home Screen Background Settings application replaces the home screen CSS files with its own, which is a bad idea to begin with. In it's post installation script the application makes a backup copy of the original CSS files and overwrites them with its own. In the pre remove script it overwrites the current CSS files with the backed up files without checking whether the current CSS files are the ones it had created.
If you install this application when running PR1.1 it will make a backup copy of the PR1.1 CSS files and replace them with its own. If you then upgrade to PR1.2 or PR1.3, the standard PR1.2 or PR1.3 CSS files will be installed. If you then uninstall this application, this application will overwrite the standard PR1.2 or PR1.3 CSS files with the PR1.1 files it had backed up earlier, causing your system to run PR1.2 or PR1.3 with the PR1.1 CSS files, which will not work and will lead to serious problems.
Developers: NEVER modify any Harmattan operating system files even if you have found a loophole allowing you to do so. It WILL cause problems for end users for example during/after an operating system upgrade.
Users: Think twice before trusting non-Store content. The Store has at least some quality assurance; even if the quality assurance is not very good there are at least some criteria to which the applications are checked against. Also, when seeing problems, try remembering exactly what you have done before the problems started. This is crucial for reporting. In this case the problems appear AFTER uninstalling an application but it's still that application's fault, not any other application's!