I post this here in the hopes that it may help someone who ran into the same roadblock I ran into. I do not know if this application will work for me in the long run, but I have finally succeeded in getting it to start. I expect that I will hit other stumbling blocks in the future, which I will deal with then.
So, yes - After Effects CS5 is not supported on Mavericks, but eventually you can make it start.
What I did was the following. I do not know how much of this was necessary, but it is what I did.
1. As noted above, AECS5 had a problem at startup with renaming a file to Workspaces.xml.
I think this may be a file that is auto generated when AE starts up, given that each time I tried to startup the app, it was failing to rename a slightly differently named file to Workspaces.xml. (each one had a different number appended between the filename and the dot separating the filename extension)
2. I thought "OK, I know how to go in and give it a file named Workspaces.xml,, and perhaps that will short circuit this problem.
I was half right. After I found my way, in Terminal, to the area I wanted to add that file to, switched to superuser mode so I could do some real damage, and accomplished the task the error message changed. Instead of not being able to rename a file, it was now having an issue with parsing from that file.
Easy to understand, since it was a blank-ish file, with only a *. comment /* line included to say what it was there for.
3. So, I came here and asked the question. Got a response re: quicktime not playing nice with AE which thoroughly confused me, since there was no indication of a QT involvement in this. Still, a nice person took the time to respond to my question, and included a pair of links for my further edification. It would be rude to just ignore that. Unfortunately, as much as I appreciate the time and effort required, it did not seem, at first, as though there were any there, there.
However, I did continue reading, and then saw another link along side my original post where there had not been anything listed under similar threads before.
I followed the first one, and it seemed to suggest that permissions were involved, which seemed logical, given the original "failed to rename" error I had been receiving. The article recommended giving my preferences files read and write permissions, which I was hesitant to do, particularly when there was no real info regarding who or whay exactly to give those permissions to.
Aside: typically, permissions are assigned on an account by account basis, or to group. U G O (User - me Group - those added as members of a work group by me, the U ser and Other - everyone else)
So, giving permission to read and write to all of the above seemed a bad idea, but since I was skeptical of the idea that this might magically clear up the problem I had with just starting up AECS5 at all, and because I affect a devil may care attitude in general, I decided "Fine, I will just give the world these permissions... at least I am not making these universally X (executable) (as if that makes any diff) ,
So, again I switched to superuser mode, and gave all groups read and write permissions (chmod ugo+rw Permissions/ )
Then I clicked on the AE icon in the dock, and - Ta Da - it did not start.
So, I altered the chmod command slightly, to chmod ugo+rw -R Permissions/ - to make it recursive, and truly give the world permission to read and write to all of my Preferences, once they all hack in to my system.
So, bottom line is, I do not yet know how messed up the rest of my system is, due to these permission changes on my preferences files for everything installed here, but After Effects CS5 is now started up on my system.
Thank you, Todd, for the response and the noodge I needed to get this resolved.