Idk if it actually will help but to me, it sounds like your UserSettings.xml was changed.
1. Open your WinExplorer
2. Type %appdata% into your adress bar
3. Go to Roaming\Need for Speed World\Settings and open UserSettings.xml with notepad (backup first!)
4. Search for <VideoConfig> and add:
<particlesystemenable Type="int">1</particlesystemenable>
at the end of the VideoConfig section.
5. Save & Close the file/notepad
Now it should work again, at least it did for me, when I had this problem (after playing around with the UserSettings.xml)
Edit: You can change some graphic-options with this file, which can help you to optimize your game for you. F.e. if you don´t like the motion blur you can turn it off with this line:
<motionblurenable Type="int">0</motionblurenable>
Just in case some people didn´t know about. Here are 2 links which go deeper into this:
