with the exception of eCart 5, The stand alone extensions are not compatible with DW CS6, The stand alone extensions have been replaced by Data Bridge and Design Extender.
I would suggest contacting the sales department, they will be able to give you an upgrade price for upgrading to design Extender and Data Bridge, depending on your purchase history, you may qualify for as low as $39.99 upgrade for design extender, and $149 for Data Bridge.
as for the errors you are getting, i would suggest recreating the users configuration folder.
for help locating the configuration folder, see the Common Installation issues page:
once located, make sure DW and the extension manager are closed and rename it. When you re once DW or the Extension manager it will be recreated.