I've used Logmein hamachi for years without problems. Usually I use ti to spoof a LAN connection, so i can play Minecraft in "lan" mode with a friend.
Recently it hasn't worked. Everything looks fine, I can join my friend's network and he can join mine, I hover over his name and it says "direct tunnel" and his name bubble thing is green with wobbles either side of it as usual. but when I right click and select ping: Request timed out. Over and over.