I didn't have an SD card in, but did have several external hard drives connected. Disconnected everything and HX Edit worked. Still working today, even with everything re-connected. Fingers crossed.
I am having the same problem. Latest version downloaded, and install seems to go ok, but nothing happens when I run hx edit. I'm on windows 8. Never had a problem with an update before. Tried several times, re-downloaded, re-booted etc.