Just upgraded to Windows 10. Now when I try to start Cardhunter, it hangs on the first screen for awhile, then gives the message, Received an invalid response while authenticating: Try again? When I click Yes, it opens a box that says Select a Cardhunter Account, but no accounts are listed and I can't do anything at all at that point. Do I just need to reinstall? I'm using Steam. Thanks!
This happened because of problems Steam was having (see here: http://forums.cardhunter.com/threads/intermittent-steam-login-problems.7776/), it's not related to Windows 10. You just happened to install it when Steam glitched.