Just installed (a few days ago) the latest 4.3 build dated June 6 2014 for 64bit version. I can no longer edit registry values. See attachment for a picture of the error dialog that pops up when I attempt to change a value.
Now, between the time that I installed the latest MC and today, a Windows 7 update was also pushed to my machine and installed. So I'm not 100% sure that MC is the cause of the problem. But if it's not, I don't know where to look to fix it.
I can not make this happen.
But I have made some changes around the plugin execute of items so if might be fixed without me knowing it was broken.
Just installed the latest beta update the registry edit problem is fixed.