For anyone on Windows, Mac, or Linux using COE’s Cloud Sync to sync files across multiple devices, a new version (1.3.0) was released on June 25th, 2013. Updating is easy — visit the OwnCloud Sync Client page, download the latest version, and run the installer. You will be asked to uninstall the old client first: please do this, but do not delete the data folder. If you do, you will have to reconfigure the server settings.
I just updated the client on two computers, and the new client immediately ‘just worked’. As always, if you run into any trouble, we’re here to help!