I found the same problem and thanks to this post i solved it.
I have my Extension Manager in spanish, and my flash CS4 in english. So, the Extension Manager install the Gaia extension in a Spanish directory located at:
C:\Users\my_name_user\AppData\Local\Adobe\Flash CS4\es\Configuration
But the destination must be:
C:\Users\my_name_user\AppData\Local\Adobe\Flash CS4\en\Configuration
So, I searched all new files in "/es/Configuration" directory and I copied these files in "/en/Configuration"
At the moment, i don't know if i do something wrong but, at least, now I can see GAIA Panel.

Is important to check the language version of Extension Manager and Flash...