For starters I'm hearing the servers are down again. However, to get past that error turn off compatibility mode. If you still get it make sure your AV is off. Make sure your firewall isn't blocking CA. And if that doesn't work make sure compatibility mode is off and reinstall the new patch. I've heard that if compatibility was on the patch may not have installed properly.
Nexon is getting smarter by turning off compatibility mode bcoz most of hacks can't run well without it.