I was using Windows 7 Professional.
The last version that worked was gpg4win 2.3.4 (I didn't try any beta or rc), and encryption/decryption works fine for single files.
Oct 28 2017
Oct 27 2017
I have also experience the same bug and reported it on:
Oct 5 2017
I'm not sure this is what you are looking for, but in Kleopatra latest version (3.0.0-gpg4win-3.0.0), it is possible to use ascii armor by default in all encryptions:
Make sure you check the following options in settings:
Settings > Configure Kleopatra > Crypto operations > Create signed or encrypted files as text files