RS 2005 Subscription Disabled

Hello,
I'm using SQL 2005 SP2 build 3215 x64 Enterprise (4x dualcore 8Gram)
Everything is working OK (SQL,SSIS,AS,RS) except creating data driven
subscriptions.
I have an report with an custom data source (to AS) wich is working OK.
The credentials are stored in DB, SQL Agent is working a.so.
The web services is running under NT\SYSTEM, I am connected with a
domain user which is local admin.
Report Manager web interface:
I can create "normal" subscriptions and they are working OK.
I can't create data driven subscription (there is no option to create
it). (yes, it is enterprise version, see appendix :) )
Management Studio (started on the server via Remote desktop, logged in
as a domain user in the local admin group):
Both "New Subscription" and "New Data Driven Subscription" are grayed
out (disabled).
I can see the subscription created via Report Manager but I can't access
its properties , I can only delete it.
Question:
How can I create a data driven subscription from Management Studio?
How can I get the Items (create subscription) enabled in the context menu?
What I'm doing wrong ? :)
Cheers,
Radu
APPENDIX:
select @.@.version:
Microsoft SQL Server 2005 - 9.00.3215.00 (X64) Dec 8 2007 17:58:16
Copyright (c) 1988-2005 Microsoft Corporation Enterprise Edition
(64-bit) on Windows NT 5.2 (Build 3790: Service Pack 2)
All the components SQL, AS, RS are running on the same server.I want to add that we have made some time ago an upgrade from Standard
Edition to Enterprise Edition
Maybe something get wrong with upgrading the RS?
Radu