I do not use BD-RB, but AVStoDVD is also written in VB6 and also needs a correctly registered mscomctl.ocx. And Win10 users had the same problem which you are experiencing.
The problem is that the included REG_MSCOMCTL.BAT file is not smart enough for Win10. A while ago I made an improved version for AVStoDVD which should also work for BD-RB. Download here:
https://www.sendspace.com/file/2iwmqm
I included a newer version of the OCX file, but generally the older file which comes with BD-RB should work under Win10.
Just place the ocx file and the batch file in the same folder and double-click the batch file.
This batch file will not delete mscomctl.ocx in one of the Windows system folders. If there is already an incompatible or faulty ocx present in System32 or SysWOW64 then these files will be kept. This means that after executing the batch it could happen that BD-RB will still refuse to start. In this case you have to delete all previous versions of the mscomctl.ocx file from your system folders and then execute the batch file again.
Good luck
manolito