To answer the header (topic) question, many here use Kerio firewall. I use ZoneAlarm free. I have been visiting the GRC site for a few years now. In fact, I was just there last month for a Stealth! retest. With avast! running, my computer was in full stealth mode with no ports open.
Perhaps there is some setting in the Kerio firewall you can change. I have never used Kerio so I do not really know.