Had the same error here's what I did, it might not be right but it worked for me
Go to Program Files\Stardock\SDCentral\installed\
delete sp.xml and wb5.xml
open Stardock Central and click to uninstall the 2 programs (WB5 and Skin Studio)
DO NOT click the uninstall skins check box.
It will say it can't find it and ask if you want it removed from the Stardock Central list, click YES.
Now it will let you install the updates.
All I can say is this worked for me on 2 separate occasions.