ESS4 firewall blocks sometimes my internet connection

So, I recently installed Windows 7 64bit Ultimate (Windows defender and firewall turned off). I have a cable internet connection (its always ON, no need for usernam or pass). I downloaded the trial version of ESET Smart Security 4. Everything worked fine for few hours. Then, suddenly Firefox and IE didn't want to open any site, and my Windows Live Messenger disconnected. So, basicly like there is no internet connection. I tried everything but nothing helped. Then I turned OFF the Eset Smart Security Firewall and voila - my internet worked. I put it back to ON, and everything is fine for few hours and then the same problem happens again.
Could anyone help? Thank You.