I can confirm that this appears to be fixed in 2.0.6-beta9.
Jan 11 2018
Jan 9 2018
I can confirm that PGP/MIME works ok for me.
Jan 8 2018
In the folder %APPDATA%\gnupg create a file named gpg.conf (or edit it if it exists) and put the line "ignore-mdc-error" in there. This should globally set this option and gpgol will also respect this.
Jan 5 2018
OK. Thank you for that.
Forgive me if I'm completely off the mark here. In no way do I claim to fully understand gpg etc.
Ignore my previous comment - seems that if I'm off our corporate network, I have the issue. Back on the network, Kleopatra is ok, and the gpg command completes. (I suspect that there is a firewall rule required, as the firewall is only enabled off network.)
Jan 4 2018
Tried that, and it complained that the gpg-agent was not running. Now Kleopatra fails to , constantly trying to load certificate cache. Self test fails on UiServer Connectivity. Was fine up to that point.