Hmm, well, the only other thing that comes to mind is that you are using one of the Kaserpsky versions with a firewall, and that you've told it to block 3cx, or some component of 3cx. One of those occasional "Allow/Disallow" questions answered the wrong way.
Uninstall Kaspersky, run the damanged installation removal tool, then reinstall.
http://support.kaspersky.com/faq/?qid=208279463