This article explains how to recover a file from dropbox when it has been encrypted by Cryptolocker. As cryptolocker changes the file extension for all files to “.encrypted” the original file can be found in deleted items.
On a non-infected PC logon to the dropbox website. Navigate to the folder required and click on the “show deleted files” icon
You should now be able to view the file and restore. I suggest restoring from a previous version first.
Click on a link to download the file