Same problem here....
I have Plesk 9 license, I wasn't using Plesk anymore, because is too limited and hard to keep my services updated without plesk dumb packages dependencies system.
But now, I want to install it back, just to keep using the license I already both in the past... Oh another surprise.
Your team is getting every day better! Keep that way, maybe the next license come togheter with Intel license limitations new system. What you will be possible to use some few versions of plesk in a limited options of processors. That way you make easy money
or... lose clients, whatever.
Plesk 9 is fully compatible with Centos 6.0 the auto-installer just don't work because they want sell new license, just trhow it in the face your clients, is simplier. We are here just to you take our money.
Or give a FAQ for how to bypass the your own failures, to keep us happy and give us the choise to upgrade because the new version is better not because you joined new version of BSD and other free services as supported things.
When I buy first time in Plesk 6, I dosen't know that filosofy by parallels, is so sadly, if I knowed that time, I had never buy any license, or upgrade my one some times until version 9.
You are not selling a service, you are selling a jail for your clients.