Well, there's something in your local network or on the host computer that's stopping people from connecting. Hamachi is a VPN and most likely bypasses firewalls, routers and NAT's.
There's no way to give a general solution that will work for everybody because everyone runs with different software and hardware. Here's a few ideas for troubleshooting though:
1) Close all software you don't need, if that solves the problem narrow it down app by app
2) If possible, connect straight to the modem, bypassing routers, or connect through a router/modem from a DMZ, if that solves the problem, double check the configuration on the router.