Trying an upgrade from 2.2.6 to 2.3.0, the gpg-agent was not
terminated, so c:\Program Files\GNU\GnuPG\libksba-8.dll
could not be overwritten. Used task manager to terminate gpg-agent.exe.
Then retry: worked.
On Windows 7 (DE) 32bit.
Longer explanation:
After the hint, I've used the Kleo menu to quit/stop kleo.
Expected behaviour: The gpg-agent should be terminated during the upgrade.
Even better: Kleos "Stop" also stops the background services.