UPDATE: If you ran into the “desktop effects could not be enabled” error, try one of the following:

1. Check if you have installed the recommended drivers for your video card in System -> Administration -> Additional Drivers
2. In case of NVidia cards, install the latest driver as showin in this post
3. Remove any theme-related software you installed recently. Eg: compositing managers, themes
4. Install the compiz-fusion-plugins-extra package
5. Try the command: compiz –replace
6. Completely remove all the  compiz stuff and reinstall
7. Try this: http://ubuntuforums.org/showpost.php?p=9212078&postcount=10
8. Install Ubuntu Tweak

The above are some of the methods different people around the world have solved the issue. But there’s no guarantee these may work for you.

When I switched on the laptop today evening I had no idea that I was in for a shock. All the desktop effects had gone; the desktop cube nowhere to be seen; no animations or effect whatsoever; and docky reports some compositing problem.

Then I go to my Appearance Preferences and find out that Visual Effects option has been set to None. Trying to change it resulted in the age-old problem: “Desktop effects could not be enabled”.

I do some googling and find out that I’m not alone and there’s an easy remedy, too. Just go to the Package Cleaner in Ubuntu Tweak, click Purge PPAs and purge the Compiz package out of the list. And everything’s back to normal.

No, wait. Not everything. I had once installed the extra compiz plugins package which added some cool new effects, and it’s gone missing. Apparently this and the update I did in the last boot has resulted this.

And later found out that it was actually the update that messed up the things. All you have to do is to go back to the previous version.