hi ! i post for if someone have same problem....
i installed Sunbelt Kerio Firewall personnal on my Windows 7 but during install it blocks & tells that it's incompatible with this windows.
so i canceled the install then my connection was broken......
Diagnostic -> the DNS server does not answer (le serveur DNS ne repond pas, in french)
so i searched and no trace of kerio.. but, when i went in :
Connection -> NETWORK > local network connection , right click property...
there was a f**ckin "think (lol) called "sunbelt something...."
so i deleted it, and now my conection is back.
if that can help, kerio suxx with Windows 7.. (i dont watched the total incompatibility software list coz too long)
if that can help.....
btw, if u know a good firewall for 7, tell me thx.