Dropbox sometimes chmod's random updated files to 666

Question

I have the website content on the centos 5 server saved in Dropbox. In that way i can easily access them without having to use ftp. However sometimes it happens that Dropbox chmod's random updated files to 666. This causes the error: "this file is group writeable" Why does it do that and how should i prevent it? Should i maybe create a cron script that looks for chmod 666 files and automatically corrects them? Still that would be a lousy fix though....