Sorry that I have to post here but the old thread is closed. Please post a link to this thread as other people still have my issue in my old thread: Cisco EPC3925 stops working when a wired PC is starting
I finally found the issue. The problem was BitDefender Total Security 2012. After I had some other (not related) problems with BitDefender, I bought G Data Total Protection 2013. Since I uninstalled BitDefender from all my PCs and installed G Data on all of them, it NEVER crashed again because of that issue.