For some reason, my extension manager comes up in something sounding a bit Germanic. Maybe Dutch. I've upgraded several times (now to CS6, even though my package is CS5), and that doesn't change it. Somewhere in the bowels of my Mac, there's a foreigner... Also, this seems to come up in a plugin for PS as well. No idea where it is!
What does "now to CS6, even though my package is CS5" mean? Do you mean you are using Extension Manager CS6 to manage extensions that you installed for CS5 products? Because Extension Manager cannot update automatically from CS5 to CS6, you have to uninstall Extension Manager CS5 first, and download the Extension Manager CS6 from http://www.adobe.com/exchange/em_download/, and install it manually. However, Extension Manager CS6 can manage many extensions installed for CS5 products because some extensions support multiple CS families.
Another thing you should know is, if Extension Manager is launched from the menu of CS products such as InDesign, its locale should be consistent with the locale of the product; If Extension Manager is launched standalone( for example, from launch pad or terminal ), its locale should be sonsistent with the locale of your OS. You can explicit set the locale of Extension Manager in command line( refer to http://helpx.adobe.com/content/help/en/extension-manager/using/command-line.html ):
"Aodbe Extension Manager CS6" -locale lang="en_US"