Puttygen for windows 8.1

I just had the same problem on my system. Using the same version I have been using for months, the Putty window actually pops up and captures mouse and keyboard events but is totally invisible.

I tried Right-Clicking and Moving the window but it didn't show anything except the cursor was on the Window header. Since I usually run with 2 monitors, I tried disconnecting the external monitor and when I reconnected the Putty windows would get flashed up during the screen resets. I tried rebooting but had the same problem.

Remember there has been no change in my system except some Windows Updates last night so the Putty version is not the problem.

Eventually I switched the Display Graphic Properties to 16-bit and it worked but when I ran it again in 32-bit it was invisible again.

Final solution: I found that by changing the compatibility settings (Right-Click on the Executeable File Icon and click on Properties. Then in the Compatibility) to Disable desktop composition. And so far so good. Display back to 32 colours.

BTW: For those saying to use WinSCP, it is not a complete replacement for Putty since it does not do Serial connections, not even USB to serial like what you need with say Cisco routers and switches, Arduinos or FTDI connected devices.