As far as I know, as long as your operating system and computer hardware can handle AE CS4, you should have no technical issues with installing the new version.
If you have questions about upgrade pricing from 6.5 to CS4, you'll have to talk to Adobe.
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.
Michael's absolutely right about the hardware-operating system deal.
You need to go to the Adobe web site and look at the AE System Requirements. Do it before you even consider the upgrade. If your computer was brand-new when you installed AE 6.5, you could be dead-ended, and you'll face a lot of other choices before you can upgrade.
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA