Can't Edit Office 365 SharePoint Site Using SharePoint Designer

When we want to EDIT Office 365 SharePoint Site Using SharePoint Designer, we are getting unexpected error.

When we click OK it will "The Server couldn't complete the request". 

This error happens when we OPEN root site, we can OPEN sub sites using SharePoint Designer.

This is a problem with SharePoint Designer. We have to install Service Pack 1 for SharePoint Designer. (KB 2817441)

After Restart the server, we can OPEN the Office 365 SharePoint Site Using Designer.