UPDATE - March 15: The latest version of Boxifier fixes this issue.
Razvan from Boxifier here.
After investigating several reports from our users we found out that Kaspersky Internet Security prevents Dropbox from running when Boxifier is installed.
Our initial analysis found out that this is caused by a bug in Kaspersky Internet Security.
The only solution for now is to disable Kaspersky and restart the computer, but our team is looking into finding a workaround for this and/or getting Kaspersky to help with fixing the issue.
This thread will be updated with more information soon. In the meantime, please get in touch if you have any questions: firstname.lastname@example.org