Did you actually try opening them in CS4?
Sorry, you can't.
For my information... (academic only)
You are saying...one cant open a CS5 AEFX project in CS4 at all ???
(I am aware you cant Save it as a CS4 project because an option is not available.)
Is it a 64 bit thing or something else?
Nope. Not at all. It has been this way for all versions of After Effects. If you have two versions open on the same machine, you can do a very limited copy and paste operation to get some elements across. That can be better than nothing in a pinch.
We have come close to implementing the ability to save backwards a few times, but it's a lot of work, and we haven't had enough interest expressed to quite justify the work. That's why I stress the feature requests especially in this case.
In my case I would be wanting to go the other direction anyway. ie CS3/4 to CS5.
> In my case I would be wanting to go the other direction anyway. ie CS3/4 to CS5.
That direction works fine.
how can we save down files from CS5 to CS4 ?
And just to add one more confirmation: You can't. If you wanna keep your clients and make them happy, just upgrade to CS5. At this point even most plug-in vendors have caught up, so there is for the most part nothing to fear...