I have the same problem on Windows 8. My Windows 7 setup does just fine. The Windows 7 only reset when software was updated, So I turned auto update to notify only.
The only thing I found on the Zello website that said would fix this is going to tools, options, connections, Check use TCP connection, But that did not work for me.
squadman & KLM who is your ISP.
My Windows 7 machine is on AT&T & the Windows 8 machine is on Comcast. I would like to know if Comcast is causing out problem.