Moving this discussion to the Extension Manager forum.
One thing you have to know: That you are administrator doesn't means that all applications you are running have administrative privilege automatically, no matter Windows or Mac. You have to explicitly tell OS (Windows or Mac) you want to run applications as admin. on Mac, sudo command should be used.
1. Run "/Applications/Utilities/Terminal.app".
2. Input the following commnad then press "return" key.
sudo "/Applications/Adobe Extension Manager CS5/Adobe Extension Manager CS5.app/Contents/MacOS/Adobe Extension Manager CS5"
3. Input your admin password then press "return"key.
BTW, privilege escalation feature was introduced in CS5.5. So in CS5.5 and later, you don't have to run EM this way.
Thank you so much Carl, that did the trick, you saved me many hours. Is there a way to do this without running the terminal command?
For others having similar problems, I also had to install this patch in order to RE-install the extension:
There is no simpler way to do this in CS5. The alternative way is to grant write permission to yourself for all folders where the extensions will be installed, which is more complicated.
for windows user.
type adobe extension manager (start/search field) when it listed out- right click and choose RUN AS ADMINISTRATOR
browse your extensions. and install