You would need to use a 64 bit plug-in with the 64 bit version of MC. And 32 with 32. Is that the problem?
No, no, as kr4 said below.
Sure we use proper version.
It is hard to believe the bug is in JRiver, I think it is either in the interface (maybe unexpected flow of events) of the VST3 module of Dirac
What I am saying is that Dirac promised to release a new version in March, so it might be a good idea it will be 'certified' to work under JRiver