Using EndNote via Dropbox
The creators of EndNote (Thompson Reuters) do not recommend using EndNote libraries stored in cloud based services, i.e.
"Dropbox is a cloud based file sharing service. Our database products (EndNote, Reference Manager and ProCite) were not designed for compatibility with this service or other cloud storage. While you can use the service to keep a backup copy or share a compressed copy of your database file(s), we do not recommend opening and/or using the database from that location. If you have your database files saved to Dropbox or any cloud storage, we recommend you copy the files to another location on your computer or remote drive before you open them.
Some of the other cloud storage services that would cause this issue include Sharepoint, Google Drive and iCloud."
At CSU we have encountered a number of users with corrupt EndNote libraries ... caused by the use of Dropbox.
If you plan to use EndNote on multiple computers we normally recommend the use of a portable USB drive for your working EndNote library. Backing up your library regularly to a computer.
EndNote X6 provides improved integration with the cloud based EndNote Web (free to CSU staff and students) and provides another option for syncing you EndNote library across multiple computers - see http://libguides.csu.edu.au/endnote