There was an error in the server update file on our web server that was causing a problem with downloading the server update for 5.17.4.
If you were trying to update to 5.17.4 using the Application Updates feature (including automatic updates) then you would have gotten 5.17.3 instead! Very annoying.
The error in the server update file has been fixed so you should now be able to install the server update successfully.
Thank you to those who reported this issue to us.
We apologize for any inconvenience this may have caused.