Hi,
I succeeded to remove this problem by uninstalling first Visual Studio 2015 (Isolated shell) and then run the Cakewalk install from BandLabAssistant.
After I had uninstalled VS 2015 I did not any more get this error message (Unable to register DLL/OCX: RegSvr32 failed with exit code 0x3) and Cakewalk installation was completed perfectly!
Seems that somehow there is conflict between Cakewalk installer and VS2015 shell?
I had the VS2015 shell on my computer as I was using Atmel Studio 7.0, and Atmel Studio needs VS2015 shell to work. At the moment Atmel Studio doesn't start due to that.
I haven't yet try to install VS2015 shell back to get Atmel Studio to work (I don' t need to use it at the moment).
Hope that this info can help somebody with same problem.
/Jouko
