Now, I tried to read through all of these so my apologies if someone said this somewhere. I've had this same issue off and on since the NA servers went up but for me the issue was to always exit out and then open it up again.
Now, that may seem simple enough BUT unless you toggle a certain setting in the client settings then when you hit the big "X" in the top right corner of the client, it minimizes instead of closing out fully. In my case, going to task manager and closing all Gameforge processes from there and then restarting the client works for me. It may or may not fix your issues but I just wanted to make sure that it is known that this might be a possible solution.
Click on your little account drop down in the client > Settings > Client Settings > Close button exits the Gameforge Client
This worked for me. As you said, you need to make sure all the Gameforge processes are shut down. Otherwise, you end up stuck with the same error.
After closing everything down, I restarted the client, which then auto-updated and BAM, the problem went away. The tricky part is that it can look like you closed it, but in fact it's still running in the background!
) workplace and start launcher without any warnings. I think that "someone tuned security through ass-hole"!!! 
