Hi there, I have experienced this problem a couple of times, I wake up one day and my Windows Explorer jumplists - a single feature I love so much about windows 7, just disappears. First time it happened, I fixed it by recreating another user account... That got it working again  but meant I had to start recreating all my favourite preferences again.

Now there is an even easier method. To fix your disappeared jumplists, simply follow the steps below:

1. Click and open Windows Explorer 
2. Now, copy and paste this address to Windows Explorer address bar: %AppData%\Microsoft\Windows\Recent\AutomaticDestinations 
3. A list of files will appear on the window. 
4. Locate the files which are unusually larger. Delete them. 
5. Voila! Jumplists working like new.

Sometimes I delete all the files and and it fixes it too but I loose Jumplists in other applications. So its worth the effort to locate the larger files first before deleting...

Enjoy