I have the same problems as reported in this topic;
http://myrobotlab.org/content/no-serial-port-found
unfortunately the proposed solutions don't seem to be working for me. Hunted for zombies (weren't there), reinstalled drivers (to no avail) and even tried different arduino boards (after going through 2 different megas, 3 chinese knockoff unos and an official uno, I think I can safely exclude board).