The spelling check cannot be completed because there is no dictionary installed for the current language

If you are receiving the following error trying to use the spell check feature in SharePoint 2010 or SharePoint 2013, chances are the issue is due to insufficient security permission on an installation folder.

This feature requires that the <server name>\Users group on the local server has Read permission to the OFFICE14/OFFICE15 folder in your installation path.  Windows grants this permission to the root of the drive by default, so if it’s missing in your installation it’s likely due to security hardening on the local server. 

To resolve the issue, grant the <server name>\Users group at least Read permission to the <drive>:\Program Files\Microsoft Office Servers\OFFICE14\ or <drive>:\Program Files\Microsoft Office Servers\OFFICE15\ directory.  Here is a snippet of what the default permissions for the <server name>\Users group looks like on a SharePoint 2013 installation, installed on the F: drive.