Apple just released version 10.10.1 of OS X Yosemite with the following changes : - Improves Wi-Fi reliability - Improves reliability when connecting to a Microsoft Exchange Server. - Improves reliability sending Mail messages when using certain email service providers. - Improves reliability when connecting to remote computers using Back to My Mac. Go get the update or the full Yosemite download from the Mac App Store or https://itunes.apple.com/us/app/os-x-yosemite/id915041082