After installing the BB10 SDK you might run into the problem that your already existing PlayBook SDK on the same Win 8 computer can't create debug tokens and won't sign your PlayBook apps anymore.
Metaviewsoft found out that you can create your debug token for the PlayBook with the BB10 SDK, but that trick doesn't help with the signing. The PlayBook SDK doesn't find its signing keys (a.k.a. author.p12, ...) even while the BB10 SDK does. Unfortunately you can't use the BB10 SDK to sign your PlayBook apps. The Reason
It turns out that the Playbook SDK is searching for the signing keys in the wrong location. The PlayBook SDK expects the keys in:
C:\Users\YourUser\Local Settings\Application Data\Research In Motionwhile the BB10 SDK stores and expects the keys in:
C:\Users\YourUser\AppData\Local\Research In MotionHere is the catch:
On Englisch Win8 systems both directories are identical because Windows 8 creates a hard link for the Local Settings\Application Data directory which maps it to the new location. But on non Englisch systems this directory is localized and the hard link is localized as well.
So on my German Windows there is a hard link for Lokale Einstellungen only but not for the Local Settings directory. The Solution
Just create the missing directory structure Local Settings\Application Data\Research In Motion in you user directory and copy the 3 signing files author.p12, barsigner.csk and barsigner.db over and your old PlayBook SDK will happily sign your apps again. Thanks DementiDevel for pointing me into the right direction.