I'm having an issue too. I don't know what yours is, but I'm getting a Error 10600, -2 code. And from what I remember back in the summer time, that's the ban code. Are you getting any error codes popping up? or is just stopping at the version checking screen, failing to get to the launch screen?
EDIT: You may have to do more then a reinstall using the original downloaded file. Sometimes, like right now, you'll have to uninstall, delete the Nexon files, and I've had to redownload a fresh version of CA (wtf that does, I don't know).
Also, were you using any hacks before this occured (this is for my personal question, ive never used speed hacks, and just did for the first time)