I have the same problem and I answer to your question: no, I'm not using DM.
- I have the plug-in installed
- I login in the app world and I ask to download an app.
- first step is thicked (Get the BlackBerry App World Browser Plug-in)
- for the second step (Connect your smartphone) I select my device in the drop-down list and regardless what I choose in the screen in my 9100 with OS6 (Charge only, Sync Media, USB drive) I get the message error
I really don't know how to sort it out !!!
PS I get the same result regardless the browser (Firefox, Chrome or IE)