Apple Remote Desktop 3.9 Update problems? If you run Apple Remote Desktop Admin you will notice Apple has recently released version 3.9.

If, as happened to me, your AppStore does not display the update to the Apple Remote Desktop Client update as well as the Apple Remote Desktop Admin upgrade, and you upgrade your Apple Remote Desktop Admin first, these bad things will happen: 


You will not be able to open Apple Remote Desktop Admin on your machine, because your client is not the right version.


If you run the AppStore again and pick up the ARD Client updater, you can open ARD Admin again, but


You will lose the ability to send Unix commands, install packages, etc to all computers you manage that have not yet upgraded to ARD client 3.9


If you upgrade your remote clients to ARD Client 3.9 by whatever means, you will get back control of them through your ARD Admin but,


The ARD Client version 3.9 is not compatible with any OS below Yosemite!


If you run clients running an OS older than Yosemite, you will only have Screen Sharing access to those clients forever more (or until a legacy patch is written).

Anyone with Apple Remote Desktop Admin 3.8.5 can still do all of the remote goodness to ARD Clients running version 3.9. 

TL;DR, if you upgrade your Apple Remote Desktop Admin to version 3.9, you will have a bad time.

Can anyone suggest a workaround, other than "don't upgrade to Apple Remote Desktop Admin 3.9"?
One thing that helps is that there is a compatibility mode in the Security Tab of the Preferences.