I have CS6 and I had to install CS5.5 after to edit an old job. Now I have 2 versions of Extendscript Toolkit : 184.108.40.206 (CS6) and 220.127.116.11 (CS55).
My problem is that EST for CS6 is not able to "link" with Indesign CS6. The little link is greyed when I choose it as target and I can't load the Indesign object model in the Object Explorer . I can choose it in the older version though of Extendscript Toolkit and in its Object Explorer.
How can I make the version 18.104.22.168 the default version to develop scripts?
Basically you will have to uninstall both and reinstall the apps in the correct order. Installing out of order rewrites some of the shared libraries to the older version.