It seems like you are doing this correctly if you have updated the files in PowerStore with the new files here:
showthread.php?t=12820
I would suggest that you follow these steps for recreating the configuration folder so that you can have a fresh extension manager and re-install the extensions. This should stop the error from occurring.
showpost.php?p=12293&postcount=2
Please post back after trying these things and let us know if the issue persists.