Problem: Open the client and get an error popup with no description or message and client runs as a pure white screen or not at all.
Caused by: One of Microsoft’s Windows 10 updates.
Solution: The only solution I have found so far is to remove the update. Security Update (KB3132372)
Uninstalling the update isn’t very hard and fixes the problem in 2 seconds, but it’s still annoying.
To do this go to Programs and Features. View Installed Updates on the left. Find the one matching the above and double click and say yes. Done. Conquer should work without even needing to restart.

Will post if I find a fix without uninstalling the update.

Thanks Microsoft.
Way to break something that has worked flawlessly on every OS since Windows 95.

I did some research and found that the update (released for win 10 December 29th) changes something with flash player.
Retail CO has the same issue (unsolved other than removing the update), hundreds (probably thousands) of other programs, including big names like Skype (which ironically is owned by microsoft), no longer work with the update installed.

So yeah… just remove the update and hopefully microsoft will release a better update that doesn’t break everything.