Still having the same issues.
I've removed SEP using Symantec's cleanwipe utility and there is no trace of it on the system.
I've re-configured Windows defender and excluded all JRiver folders and files everywhere on the system. I have also excluded folders used for media, tv recording, and anything else that is part of the MC library.
The only exclusions I have not made are for file types, but I can't see that making any difference in this instance.
I still have the exact same issue - MC30 starts and appears fine, but as soon as you click in the interface it hangs. If you click a second time, the MC screen gets greyed out and the Windows dialog box appears saying MC is unresponsive with options to close the program or wait for it to respond.
MC29 continues to work flawlessly. Is there anything else I can try?
I'm certain it isn't the AV, and have never had any issues with previous versions of MC on this machine whether using AV or not.
Is there an MC log file somewhere I can take a look at?